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x86/pvm: Preload user_pgd in load_pgtbl hypercall #15

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Merged
merged 1 commit into from
Dec 31, 2024
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x86/pvm: Preload user_pgd in load_pgtbl hypercall #15

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44 changes: 44 additions & 0 deletions arch/x86/kvm/pvm/pvm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,9 @@ MODULE_LICENSE("GPL");
static bool __read_mostly enable_cpuid_intercept = 0;
module_param_named(cpuid_intercept, enable_cpuid_intercept, bool, 0444);

static bool __read_mostly enable_pgtbl_preload = 0;
module_param_named(pgtbl_preload, enable_pgtbl_preload, bool, 0444);

static bool __read_mostly is_intel;

static unsigned long host_idt_base;
Expand Down Expand Up @@ -593,6 +596,22 @@ static int host_pcid_free_uncached(struct vcpu_pvm *pvm)
return -1;
}

static int host_pcid_find(struct vcpu_pvm *pvm, u64 root_hpa)
{
struct host_pcid_state *tlb_state = this_cpu_ptr(&pvm_tlb_state);
int i;

/* find if it is allocated. */
for (i = 0; i < NUM_HOST_PCID_FOR_GUEST; i++) {
struct host_pcid_one *tlb = &tlb_state->pairs[i];

if (tlb->root_hpa == root_hpa && tlb->pvm == pvm)
return index_to_host_pcid(i);
}

return 0;
}

/*
* Get a host pcid of the current pCPU for the specific guest pgd.
* PVM vTLB is guest pgd tagged.
Expand Down Expand Up @@ -745,6 +764,27 @@ static bool check_switch_cr3(struct vcpu_pvm *pvm, u64 switch_host_cr3)
return true;
}

static void pvm_pgtbl_preload_for_guest_with_host_pcid(struct vcpu_pvm *pvm, u64 *switch_host_cr3)
{
u32 host_pcid;
u64 hw_cr3;
u64 prev_root_hpa = pvm->vcpu.arch.mmu->prev_roots[0].hpa;

if (enable_pgtbl_preload &&
VALID_PAGE(prev_root_hpa) &&
pvm->vcpu.arch.mmu->prev_roots[0].pgd == pvm->msr_switch_cr3 &&
*switch_host_cr3 != pvm->msr_switch_cr3) {
host_pcid = host_pcid_find(pvm, prev_root_hpa);
if (host_pcid) {
hw_cr3 = prev_root_hpa | host_pcid;
this_cpu_write(cpu_tss_rw.tss_ex.umod_cr3, hw_cr3 | CR3_NOFLUSH);
*switch_host_cr3 = hw_cr3 | CR3_NOFLUSH;
}
}

return;
}

static void pvm_set_host_cr3_for_guest_with_host_pcid(struct vcpu_pvm *pvm)
{
u64 root_hpa = pvm->vcpu.arch.mmu->root.hpa;
Expand All @@ -760,6 +800,7 @@ static void pvm_set_host_cr3_for_guest_with_host_pcid(struct vcpu_pvm *pvm)
if (is_smod(pvm)) {
this_cpu_write(cpu_tss_rw.tss_ex.smod_cr3, hw_cr3 | CR3_NOFLUSH);
switch_host_cr3 = this_cpu_read(cpu_tss_rw.tss_ex.umod_cr3);
pvm_pgtbl_preload_for_guest_with_host_pcid(pvm, &switch_host_cr3);
} else {
this_cpu_write(cpu_tss_rw.tss_ex.umod_cr3, hw_cr3 | CR3_NOFLUSH);
switch_host_cr3 = this_cpu_read(cpu_tss_rw.tss_ex.smod_cr3);
Expand Down Expand Up @@ -1853,6 +1894,9 @@ static int handle_hc_load_pagetables(struct kvm_vcpu *vcpu, unsigned long flags,
if (cr4 != vcpu->arch.cr4) {
vcpu->arch.cr4 = cr4;
kvm_mmu_reset_context(vcpu);
} else if (enable_pgtbl_preload) {
// try to preload user_pgd.
kvm_mmu_new_pgd(vcpu, user_pgd);
}

kvm_mmu_new_pgd(vcpu, pgd);
Expand Down