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KVM: arm/arm64: Limit icache invalidation to prefetch aborts 

We've so far eagerly invalidated the icache, no matter how
the page was faulted in (data or prefetch abort).

But we can easily track execution by setting the XN bits
in the S2 page tables, get the prefetch abort at HYP and
perform the icache invalidation at that time only.

As for most VMs, the instruction working set is pretty
small compared to the data set, this is likely to save
some traffic (specially as the invalidation is broadcast).

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
This commit is contained in:
Marc Zyngier 2017-10-23 17:11:19 +01:00 committed by Christoffer Dall
parent fefb876b9b
commit d0e22b4ac3
5 changed files with 43 additions and 8 deletions
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12
arch/arm/include/asm/kvm_mmu.h
View File

@ -85,6 +85,18 @@ static inline pmd_t kvm_s2pmd_mkwrite(pmd_t pmd)
return pmd;
}
static inline pte_t kvm_s2pte_mkexec(pte_t pte)
{
pte_val(pte) &= ~L_PTE_XN;
return pte;
}
static inline pmd_t kvm_s2pmd_mkexec(pmd_t pmd)
{
pmd_val(pmd) &= ~PMD_SECT_XN;
return pmd;
}
static inline void kvm_set_s2pte_readonly(pte_t *pte)
{
pte_val(*pte) = (pte_val(*pte) & ~L_PTE_S2_RDWR) | L_PTE_S2_RDONLY;

4
arch/arm/include/asm/pgtable.h
View File

@ -102,8 +102,8 @@ extern pgprot_t pgprot_s2_device;
#define PAGE_HYP_EXEC _MOD_PROT(pgprot_kernel, L_PTE_HYP | L_PTE_RDONLY)
#define PAGE_HYP_RO _MOD_PROT(pgprot_kernel, L_PTE_HYP | L_PTE_RDONLY | L_PTE_XN)
#define PAGE_HYP_DEVICE _MOD_PROT(pgprot_hyp_device, L_PTE_HYP)
#define PAGE_S2 _MOD_PROT(pgprot_s2, L_PTE_S2_RDONLY)
#define PAGE_S2_DEVICE _MOD_PROT(pgprot_s2_device, L_PTE_S2_RDONLY)
#define PAGE_S2 _MOD_PROT(pgprot_s2, L_PTE_S2_RDONLY | L_PTE_XN)
#define PAGE_S2_DEVICE _MOD_PROT(pgprot_s2_device, L_PTE_S2_RDONLY | L_PTE_XN)
#define __PAGE_NONE __pgprot(_L_PTE_DEFAULT | L_PTE_RDONLY | L_PTE_XN | L_PTE_NONE)
#define __PAGE_SHARED __pgprot(_L_PTE_DEFAULT | L_PTE_USER | L_PTE_XN)

12
arch/arm64/include/asm/kvm_mmu.h
View File

@ -173,6 +173,18 @@ static inline pmd_t kvm_s2pmd_mkwrite(pmd_t pmd)
return pmd;
}
static inline pte_t kvm_s2pte_mkexec(pte_t pte)
{
pte_val(pte) &= ~PTE_S2_XN;
return pte;
}
static inline pmd_t kvm_s2pmd_mkexec(pmd_t pmd)
{
pmd_val(pmd) &= ~PMD_S2_XN;
return pmd;
}
static inline void kvm_set_s2pte_readonly(pte_t *pte)
{
pteval_t old_pteval, pteval;

4
arch/arm64/include/asm/pgtable-prot.h
View File

@ -60,8 +60,8 @@
#define PAGE_HYP_RO __pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_RDONLY | PTE_HYP_XN)
#define PAGE_HYP_DEVICE __pgprot(PROT_DEVICE_nGnRE | PTE_HYP)
#define PAGE_S2 __pgprot(PROT_DEFAULT | PTE_S2_MEMATTR(MT_S2_NORMAL) | PTE_S2_RDONLY)
#define PAGE_S2_DEVICE __pgprot(PROT_DEFAULT | PTE_S2_MEMATTR(MT_S2_DEVICE_nGnRE) | PTE_S2_RDONLY | PTE_UXN)
#define PAGE_S2 __pgprot(PROT_DEFAULT | PTE_S2_MEMATTR(MT_S2_NORMAL) | PTE_S2_RDONLY | PTE_S2_XN)
#define PAGE_S2_DEVICE __pgprot(PROT_DEFAULT | PTE_S2_MEMATTR(MT_S2_DEVICE_nGnRE) | PTE_S2_RDONLY | PTE_S2_XN)
#define PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_VALID) | PTE_PROT_NONE | PTE_RDONLY | PTE_PXN | PTE_UXN)
#define PAGE_SHARED __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)

19
virt/kvm/arm/mmu.c
View File

@ -1292,7 +1292,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
unsigned long fault_status)
{
int ret;
bool write_fault, writable, hugetlb = false, force_pte = false;
bool write_fault, exec_fault, writable, hugetlb = false, force_pte = false;
unsigned long mmu_seq;
gfn_t gfn = fault_ipa >> PAGE_SHIFT;
struct kvm *kvm = vcpu->kvm;
@ -1304,7 +1304,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
unsigned long flags = 0;
write_fault = kvm_is_write_fault(vcpu);
if (fault_status == FSC_PERM && !write_fault) {
exec_fault = kvm_vcpu_trap_is_iabt(vcpu);
VM_BUG_ON(write_fault && exec_fault);
if (fault_status == FSC_PERM && !write_fault && !exec_fault) {
kvm_err("Unexpected L2 read permission error\n");
return -EFAULT;
}
@ -1398,7 +1401,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
kvm_set_pfn_dirty(pfn);
}
clean_dcache_guest_page(vcpu, pfn, PMD_SIZE);
invalidate_icache_guest_page(vcpu, pfn, PMD_SIZE);
if (exec_fault) {
new_pmd = kvm_s2pmd_mkexec(new_pmd);
invalidate_icache_guest_page(vcpu, pfn, PMD_SIZE);
}
ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
} else {
@ -1410,7 +1417,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
mark_page_dirty(kvm, gfn);
}
clean_dcache_guest_page(vcpu, pfn, PAGE_SIZE);
invalidate_icache_guest_page(vcpu, pfn, PAGE_SIZE);
if (exec_fault) {
new_pte = kvm_s2pte_mkexec(new_pte);
invalidate_icache_guest_page(vcpu, pfn, PAGE_SIZE);
}
ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, flags);
}