linux/arch/x86/kvm/x86.h
David Woodhouse 451a707813 KVM: x86/xen: improve accuracy of Xen timers
A test program such as http://david.woodhou.se/timerlat.c confirms user
reports that timers are increasingly inaccurate as the lifetime of a
guest increases. Reporting the actual delay observed when asking for
100µs of sleep, it starts off OK on a newly-launched guest but gets
worse over time, giving incorrect sleep times:

root@ip-10-0-193-21:~# ./timerlat -c -n 5
00000000 latency 103243/100000 (3.2430%)
00000001 latency 103243/100000 (3.2430%)
00000002 latency 103242/100000 (3.2420%)
00000003 latency 103245/100000 (3.2450%)
00000004 latency 103245/100000 (3.2450%)

The biggest problem is that get_kvmclock_ns() returns inaccurate values
when the guest TSC is scaled. The guest sees a TSC value scaled from the
host TSC by a mul/shift conversion (hopefully done in hardware). The
guest then converts that guest TSC value into nanoseconds using the
mul/shift conversion given to it by the KVM pvclock information.

But get_kvmclock_ns() performs only a single conversion directly from
host TSC to nanoseconds, giving a different result. A test program at
http://david.woodhou.se/tsdrift.c demonstrates the cumulative error
over a day.

It's non-trivial to fix get_kvmclock_ns(), although I'll come back to
that. The actual guest hv_clock is per-CPU, and *theoretically* each
vCPU could be running at a *different* frequency. But this patch is
needed anyway because...

The other issue with Xen timers was that the code would snapshot the
host CLOCK_MONOTONIC at some point in time, and then... after a few
interrupts may have occurred, some preemption perhaps... would also read
the guest's kvmclock. Then it would proceed under the false assumption
that those two happened at the *same* time. Any time which *actually*
elapsed between reading the two clocks was introduced as inaccuracies
in the time at which the timer fired.

Fix it to use a variant of kvm_get_time_and_clockread(), which reads the
host TSC just *once*, then use the returned TSC value to calculate the
kvmclock (making sure to do that the way the guest would instead of
making the same mistake get_kvmclock_ns() does).

Sadly, hrtimers based on CLOCK_MONOTONIC_RAW are not supported, so Xen
timers still have to use CLOCK_MONOTONIC. In practice the difference
between the two won't matter over the timescales involved, as the
*absolute* values don't matter; just the delta.

This does mean a new variant of kvm_get_time_and_clockread() is needed;
called kvm_get_monotonic_and_clockread() because that's what it does.

Fixes: 5363952605 ("KVM: x86/xen: handle PV timers oneshot mode")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Link: https://lore.kernel.org/r/20240227115648.3104-2-dwmw2@infradead.org
[sean: massage moved comment, tweak if statement formatting]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-03-04 16:22:32 -08:00

548 lines
15 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef ARCH_X86_KVM_X86_H
#define ARCH_X86_KVM_X86_H
#include <linux/kvm_host.h>
#include <asm/fpu/xstate.h>
#include <asm/mce.h>
#include <asm/pvclock.h>
#include "kvm_cache_regs.h"
#include "kvm_emulate.h"
struct kvm_caps {
/* control of guest tsc rate supported? */
bool has_tsc_control;
/* maximum supported tsc_khz for guests */
u32 max_guest_tsc_khz;
/* number of bits of the fractional part of the TSC scaling ratio */
u8 tsc_scaling_ratio_frac_bits;
/* maximum allowed value of TSC scaling ratio */
u64 max_tsc_scaling_ratio;
/* 1ull << kvm_caps.tsc_scaling_ratio_frac_bits */
u64 default_tsc_scaling_ratio;
/* bus lock detection supported? */
bool has_bus_lock_exit;
/* notify VM exit supported? */
bool has_notify_vmexit;
u64 supported_mce_cap;
u64 supported_xcr0;
u64 supported_xss;
u64 supported_perf_cap;
};
void kvm_spurious_fault(void);
#define KVM_NESTED_VMENTER_CONSISTENCY_CHECK(consistency_check) \
({ \
bool failed = (consistency_check); \
if (failed) \
trace_kvm_nested_vmenter_failed(#consistency_check, 0); \
failed; \
})
/*
* The first...last VMX feature MSRs that are emulated by KVM. This may or may
* not cover all known VMX MSRs, as KVM doesn't emulate an MSR until there's an
* associated feature that KVM supports for nested virtualization.
*/
#define KVM_FIRST_EMULATED_VMX_MSR MSR_IA32_VMX_BASIC
#define KVM_LAST_EMULATED_VMX_MSR MSR_IA32_VMX_VMFUNC
#define KVM_DEFAULT_PLE_GAP 128
#define KVM_VMX_DEFAULT_PLE_WINDOW 4096
#define KVM_DEFAULT_PLE_WINDOW_GROW 2
#define KVM_DEFAULT_PLE_WINDOW_SHRINK 0
#define KVM_VMX_DEFAULT_PLE_WINDOW_MAX UINT_MAX
#define KVM_SVM_DEFAULT_PLE_WINDOW_MAX USHRT_MAX
#define KVM_SVM_DEFAULT_PLE_WINDOW 3000
static inline unsigned int __grow_ple_window(unsigned int val,
unsigned int base, unsigned int modifier, unsigned int max)
{
u64 ret = val;
if (modifier < 1)
return base;
if (modifier < base)
ret *= modifier;
else
ret += modifier;
return min(ret, (u64)max);
}
static inline unsigned int __shrink_ple_window(unsigned int val,
unsigned int base, unsigned int modifier, unsigned int min)
{
if (modifier < 1)
return base;
if (modifier < base)
val /= modifier;
else
val -= modifier;
return max(val, min);
}
#define MSR_IA32_CR_PAT_DEFAULT 0x0007040600070406ULL
void kvm_service_local_tlb_flush_requests(struct kvm_vcpu *vcpu);
int kvm_check_nested_events(struct kvm_vcpu *vcpu);
static inline bool kvm_vcpu_has_run(struct kvm_vcpu *vcpu)
{
return vcpu->arch.last_vmentry_cpu != -1;
}
static inline bool kvm_is_exception_pending(struct kvm_vcpu *vcpu)
{
return vcpu->arch.exception.pending ||
vcpu->arch.exception_vmexit.pending ||
kvm_test_request(KVM_REQ_TRIPLE_FAULT, vcpu);
}
static inline void kvm_clear_exception_queue(struct kvm_vcpu *vcpu)
{
vcpu->arch.exception.pending = false;
vcpu->arch.exception.injected = false;
vcpu->arch.exception_vmexit.pending = false;
}
static inline void kvm_queue_interrupt(struct kvm_vcpu *vcpu, u8 vector,
bool soft)
{
vcpu->arch.interrupt.injected = true;
vcpu->arch.interrupt.soft = soft;
vcpu->arch.interrupt.nr = vector;
}
static inline void kvm_clear_interrupt_queue(struct kvm_vcpu *vcpu)
{
vcpu->arch.interrupt.injected = false;
}
static inline bool kvm_event_needs_reinjection(struct kvm_vcpu *vcpu)
{
return vcpu->arch.exception.injected || vcpu->arch.interrupt.injected ||
vcpu->arch.nmi_injected;
}
static inline bool kvm_exception_is_soft(unsigned int nr)
{
return (nr == BP_VECTOR) || (nr == OF_VECTOR);
}
static inline bool is_protmode(struct kvm_vcpu *vcpu)
{
return kvm_is_cr0_bit_set(vcpu, X86_CR0_PE);
}
static inline bool is_long_mode(struct kvm_vcpu *vcpu)
{
#ifdef CONFIG_X86_64
return !!(vcpu->arch.efer & EFER_LMA);
#else
return false;
#endif
}
static inline bool is_64_bit_mode(struct kvm_vcpu *vcpu)
{
int cs_db, cs_l;
WARN_ON_ONCE(vcpu->arch.guest_state_protected);
if (!is_long_mode(vcpu))
return false;
static_call(kvm_x86_get_cs_db_l_bits)(vcpu, &cs_db, &cs_l);
return cs_l;
}
static inline bool is_64_bit_hypercall(struct kvm_vcpu *vcpu)
{
/*
* If running with protected guest state, the CS register is not
* accessible. The hypercall register values will have had to been
* provided in 64-bit mode, so assume the guest is in 64-bit.
*/
return vcpu->arch.guest_state_protected || is_64_bit_mode(vcpu);
}
static inline bool x86_exception_has_error_code(unsigned int vector)
{
static u32 exception_has_error_code = BIT(DF_VECTOR) | BIT(TS_VECTOR) |
BIT(NP_VECTOR) | BIT(SS_VECTOR) | BIT(GP_VECTOR) |
BIT(PF_VECTOR) | BIT(AC_VECTOR);
return (1U << vector) & exception_has_error_code;
}
static inline bool mmu_is_nested(struct kvm_vcpu *vcpu)
{
return vcpu->arch.walk_mmu == &vcpu->arch.nested_mmu;
}
static inline bool is_pae(struct kvm_vcpu *vcpu)
{
return kvm_is_cr4_bit_set(vcpu, X86_CR4_PAE);
}
static inline bool is_pse(struct kvm_vcpu *vcpu)
{
return kvm_is_cr4_bit_set(vcpu, X86_CR4_PSE);
}
static inline bool is_paging(struct kvm_vcpu *vcpu)
{
return likely(kvm_is_cr0_bit_set(vcpu, X86_CR0_PG));
}
static inline bool is_pae_paging(struct kvm_vcpu *vcpu)
{
return !is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu);
}
static inline u8 vcpu_virt_addr_bits(struct kvm_vcpu *vcpu)
{
return kvm_is_cr4_bit_set(vcpu, X86_CR4_LA57) ? 57 : 48;
}
static inline bool is_noncanonical_address(u64 la, struct kvm_vcpu *vcpu)
{
return !__is_canonical_address(la, vcpu_virt_addr_bits(vcpu));
}
static inline void vcpu_cache_mmio_info(struct kvm_vcpu *vcpu,
gva_t gva, gfn_t gfn, unsigned access)
{
u64 gen = kvm_memslots(vcpu->kvm)->generation;
if (unlikely(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS))
return;
/*
* If this is a shadow nested page table, the "GVA" is
* actually a nGPA.
*/
vcpu->arch.mmio_gva = mmu_is_nested(vcpu) ? 0 : gva & PAGE_MASK;
vcpu->arch.mmio_access = access;
vcpu->arch.mmio_gfn = gfn;
vcpu->arch.mmio_gen = gen;
}
static inline bool vcpu_match_mmio_gen(struct kvm_vcpu *vcpu)
{
return vcpu->arch.mmio_gen == kvm_memslots(vcpu->kvm)->generation;
}
/*
* Clear the mmio cache info for the given gva. If gva is MMIO_GVA_ANY, we
* clear all mmio cache info.
*/
#define MMIO_GVA_ANY (~(gva_t)0)
static inline void vcpu_clear_mmio_info(struct kvm_vcpu *vcpu, gva_t gva)
{
if (gva != MMIO_GVA_ANY && vcpu->arch.mmio_gva != (gva & PAGE_MASK))
return;
vcpu->arch.mmio_gva = 0;
}
static inline bool vcpu_match_mmio_gva(struct kvm_vcpu *vcpu, unsigned long gva)
{
if (vcpu_match_mmio_gen(vcpu) && vcpu->arch.mmio_gva &&
vcpu->arch.mmio_gva == (gva & PAGE_MASK))
return true;
return false;
}
static inline bool vcpu_match_mmio_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
{
if (vcpu_match_mmio_gen(vcpu) && vcpu->arch.mmio_gfn &&
vcpu->arch.mmio_gfn == gpa >> PAGE_SHIFT)
return true;
return false;
}
static inline unsigned long kvm_register_read(struct kvm_vcpu *vcpu, int reg)
{
unsigned long val = kvm_register_read_raw(vcpu, reg);
return is_64_bit_mode(vcpu) ? val : (u32)val;
}
static inline void kvm_register_write(struct kvm_vcpu *vcpu,
int reg, unsigned long val)
{
if (!is_64_bit_mode(vcpu))
val = (u32)val;
return kvm_register_write_raw(vcpu, reg, val);
}
static inline bool kvm_check_has_quirk(struct kvm *kvm, u64 quirk)
{
return !(kvm->arch.disabled_quirks & quirk);
}
void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
u64 get_kvmclock_ns(struct kvm *kvm);
uint64_t kvm_get_wall_clock_epoch(struct kvm *kvm);
bool kvm_get_monotonic_and_clockread(s64 *kernel_ns, u64 *tsc_timestamp);
int kvm_read_guest_virt(struct kvm_vcpu *vcpu,
gva_t addr, void *val, unsigned int bytes,
struct x86_exception *exception);
int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu,
gva_t addr, void *val, unsigned int bytes,
struct x86_exception *exception);
int handle_ud(struct kvm_vcpu *vcpu);
void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu,
struct kvm_queued_exception *ex);
void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu);
u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn);
int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data);
int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
int page_num);
bool kvm_vector_hashing_enabled(void);
void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code);
int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type,
void *insn, int insn_len);
int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
int emulation_type, void *insn, int insn_len);
fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);
extern u64 host_xcr0;
extern u64 host_xss;
extern u64 host_arch_capabilities;
extern struct kvm_caps kvm_caps;
extern bool enable_pmu;
/*
* Get a filtered version of KVM's supported XCR0 that strips out dynamic
* features for which the current process doesn't (yet) have permission to use.
* This is intended to be used only when enumerating support to userspace,
* e.g. in KVM_GET_SUPPORTED_CPUID and KVM_CAP_XSAVE2, it does NOT need to be
* used to check/restrict guest behavior as KVM rejects KVM_SET_CPUID{2} if
* userspace attempts to enable unpermitted features.
*/
static inline u64 kvm_get_filtered_xcr0(void)
{
u64 permitted_xcr0 = kvm_caps.supported_xcr0;
BUILD_BUG_ON(XFEATURE_MASK_USER_DYNAMIC != XFEATURE_MASK_XTILE_DATA);
if (permitted_xcr0 & XFEATURE_MASK_USER_DYNAMIC) {
permitted_xcr0 &= xstate_get_guest_group_perm();
/*
* Treat XTILE_CFG as unsupported if the current process isn't
* allowed to use XTILE_DATA, as attempting to set XTILE_CFG in
* XCR0 without setting XTILE_DATA is architecturally illegal.
*/
if (!(permitted_xcr0 & XFEATURE_MASK_XTILE_DATA))
permitted_xcr0 &= ~XFEATURE_MASK_XTILE_CFG;
}
return permitted_xcr0;
}
static inline bool kvm_mpx_supported(void)
{
return (kvm_caps.supported_xcr0 & (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR))
== (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR);
}
extern unsigned int min_timer_period_us;
extern bool enable_vmware_backdoor;
extern int pi_inject_timer;
extern bool report_ignored_msrs;
extern bool eager_page_split;
static inline void kvm_pr_unimpl_wrmsr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
{
if (report_ignored_msrs)
vcpu_unimpl(vcpu, "Unhandled WRMSR(0x%x) = 0x%llx\n", msr, data);
}
static inline void kvm_pr_unimpl_rdmsr(struct kvm_vcpu *vcpu, u32 msr)
{
if (report_ignored_msrs)
vcpu_unimpl(vcpu, "Unhandled RDMSR(0x%x)\n", msr);
}
static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec)
{
return pvclock_scale_delta(nsec, vcpu->arch.virtual_tsc_mult,
vcpu->arch.virtual_tsc_shift);
}
/* Same "calling convention" as do_div:
* - divide (n << 32) by base
* - put result in n
* - return remainder
*/
#define do_shl32_div32(n, base) \
({ \
u32 __quot, __rem; \
asm("divl %2" : "=a" (__quot), "=d" (__rem) \
: "rm" (base), "0" (0), "1" ((u32) n)); \
n = __quot; \
__rem; \
})
static inline bool kvm_mwait_in_guest(struct kvm *kvm)
{
return kvm->arch.mwait_in_guest;
}
static inline bool kvm_hlt_in_guest(struct kvm *kvm)
{
return kvm->arch.hlt_in_guest;
}
static inline bool kvm_pause_in_guest(struct kvm *kvm)
{
return kvm->arch.pause_in_guest;
}
static inline bool kvm_cstate_in_guest(struct kvm *kvm)
{
return kvm->arch.cstate_in_guest;
}
static inline bool kvm_notify_vmexit_enabled(struct kvm *kvm)
{
return kvm->arch.notify_vmexit_flags & KVM_X86_NOTIFY_VMEXIT_ENABLED;
}
enum kvm_intr_type {
/* Values are arbitrary, but must be non-zero. */
KVM_HANDLING_IRQ = 1,
KVM_HANDLING_NMI,
};
static __always_inline void kvm_before_interrupt(struct kvm_vcpu *vcpu,
enum kvm_intr_type intr)
{
WRITE_ONCE(vcpu->arch.handling_intr_from_guest, (u8)intr);
}
static __always_inline void kvm_after_interrupt(struct kvm_vcpu *vcpu)
{
WRITE_ONCE(vcpu->arch.handling_intr_from_guest, 0);
}
static inline bool kvm_handling_nmi_from_guest(struct kvm_vcpu *vcpu)
{
return vcpu->arch.handling_intr_from_guest == KVM_HANDLING_NMI;
}
static inline bool kvm_pat_valid(u64 data)
{
if (data & 0xF8F8F8F8F8F8F8F8ull)
return false;
/* 0, 1, 4, 5, 6, 7 are valid values. */
return (data | ((data & 0x0202020202020202ull) << 1)) == data;
}
static inline bool kvm_dr7_valid(u64 data)
{
/* Bits [63:32] are reserved */
return !(data >> 32);
}
static inline bool kvm_dr6_valid(u64 data)
{
/* Bits [63:32] are reserved */
return !(data >> 32);
}
/*
* Trigger machine check on the host. We assume all the MSRs are already set up
* by the CPU and that we still run on the same CPU as the MCE occurred on.
* We pass a fake environment to the machine check handler because we want
* the guest to be always treated like user space, no matter what context
* it used internally.
*/
static inline void kvm_machine_check(void)
{
#if defined(CONFIG_X86_MCE)
struct pt_regs regs = {
.cs = 3, /* Fake ring 3 no matter what the guest ran on */
.flags = X86_EFLAGS_IF,
};
do_machine_check(&regs);
#endif
}
void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu);
void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu);
int kvm_spec_ctrl_test_value(u64 value);
bool __kvm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
int kvm_handle_memory_failure(struct kvm_vcpu *vcpu, int r,
struct x86_exception *e);
int kvm_handle_invpcid(struct kvm_vcpu *vcpu, unsigned long type, gva_t gva);
bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 index, u32 type);
/*
* Internal error codes that are used to indicate that MSR emulation encountered
* an error that should result in #GP in the guest, unless userspace
* handles it.
*/
#define KVM_MSR_RET_INVALID 2 /* in-kernel MSR emulation #GP condition */
#define KVM_MSR_RET_FILTERED 3 /* #GP due to userspace MSR filter */
#define __cr4_reserved_bits(__cpu_has, __c) \
({ \
u64 __reserved_bits = CR4_RESERVED_BITS; \
\
if (!__cpu_has(__c, X86_FEATURE_XSAVE)) \
__reserved_bits |= X86_CR4_OSXSAVE; \
if (!__cpu_has(__c, X86_FEATURE_SMEP)) \
__reserved_bits |= X86_CR4_SMEP; \
if (!__cpu_has(__c, X86_FEATURE_SMAP)) \
__reserved_bits |= X86_CR4_SMAP; \
if (!__cpu_has(__c, X86_FEATURE_FSGSBASE)) \
__reserved_bits |= X86_CR4_FSGSBASE; \
if (!__cpu_has(__c, X86_FEATURE_PKU)) \
__reserved_bits |= X86_CR4_PKE; \
if (!__cpu_has(__c, X86_FEATURE_LA57)) \
__reserved_bits |= X86_CR4_LA57; \
if (!__cpu_has(__c, X86_FEATURE_UMIP)) \
__reserved_bits |= X86_CR4_UMIP; \
if (!__cpu_has(__c, X86_FEATURE_VMX)) \
__reserved_bits |= X86_CR4_VMXE; \
if (!__cpu_has(__c, X86_FEATURE_PCID)) \
__reserved_bits |= X86_CR4_PCIDE; \
if (!__cpu_has(__c, X86_FEATURE_LAM)) \
__reserved_bits |= X86_CR4_LAM_SUP; \
__reserved_bits; \
})
int kvm_sev_es_mmio_write(struct kvm_vcpu *vcpu, gpa_t src, unsigned int bytes,
void *dst);
int kvm_sev_es_mmio_read(struct kvm_vcpu *vcpu, gpa_t src, unsigned int bytes,
void *dst);
int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
unsigned int port, void *data, unsigned int count,
int in);
#endif