[RFC PATCH v2 2/4] arch/x86: Refactor tlbflush and l1d flush

Balbir Singh
2020-03-25T07:11:36Z

Refactor the existing assembly bits into smaller helper functions
and also abstract L1D_FLUSH into a helper function. Use these
functions in kvm for L1D flushing.

Signed-off-by: Balbir Singh <sblbir@amazon.com>
---
arch/x86/include/asm/cacheflush.h | 3 ++
arch/x86/kernel/l1d_flush.c | 49 +++++++++++++++++++++++++++++++
arch/x86/kvm/vmx/vmx.c | 31 ++++---------------
3 files changed, 57 insertions(+), 26 deletions(-)

diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index 6419a4cef0e8..66a46db7aadd 100644
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -10,5 +10,8 @@
void clflush_cache_range(void *addr, unsigned int size);
void *alloc_l1d_flush_pages(void);
void cleanup_l1d_flush_pages(void *l1d_flush_pages);
+void populate_tlb_with_flush_pages(void *l1d_flush_pages);
+void flush_l1d_cache_sw(void *l1d_flush_pages);
+int flush_l1d_cache_hw(void);

#endif /* _ASM_X86_CACHEFLUSH_H */
diff --git a/arch/x86/kernel/l1d_flush.c b/arch/x86/kernel/l1d_flush.c
index 05f375c33423..60499f773046 100644
--- a/arch/x86/kernel/l1d_flush.c
+++ b/arch/x86/kernel/l1d_flush.c
@@ -34,3 +34,52 @@ void cleanup_l1d_flush_pages(void *l1d_flush_pages)
free_pages((unsigned long)l1d_flush_pages, L1D_CACHE_ORDER);
}
EXPORT_SYMBOL_GPL(cleanup_l1d_flush_pages);
+
+void populate_tlb_with_flush_pages(void *l1d_flush_pages)
+{
+ int size = PAGE_SIZE << L1D_CACHE_ORDER;
+
+ asm volatile(
+ /* First ensure the pages are in the TLB */
+ "xorl %%eax, %%eax\n"
+ ".Lpopulate_tlb:\n\t"
+ "movzbl (%[flush_pages], %%" _ASM_AX "), %%ecx\n\t"
+ "addl $4096, %%eax\n\t"
+ "cmpl %%eax, %[size]\n\t"
+ "jne .Lpopulate_tlb\n\t"
+ "xorl %%eax, %%eax\n\t"
+ "cpuid\n\t"
+ :: [flush_pages] "r" (l1d_flush_pages),
+ [size] "r" (size)
+ : "eax", "ebx", "ecx", "edx");
+}
+EXPORT_SYMBOL_GPL(populate_tlb_with_flush_pages);
+
+int flush_l1d_cache_hw(void)
+{
+ if (static_cpu_has(X86_FEATURE_FLUSH_L1D)) {
+ wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH);
+ return 1;
+ }
+ return 0;
+}
+EXPORT_SYMBOL_GPL(flush_l1d_cache_hw);
+
+void flush_l1d_cache_sw(void *l1d_flush_pages)
+{
+ int size = PAGE_SIZE << L1D_CACHE_ORDER;
+
+ asm volatile(
+ /* Fill the cache */
+ "xorl %%eax, %%eax\n"
+ ".Lfill_cache:\n"
+ "movzbl (%[flush_pages], %%" _ASM_AX "), %%ecx\n\t"
+ "addl $64, %%eax\n\t"
+ "cmpl %%eax, %[size]\n\t"
+ "jne .Lfill_cache\n\t"
+ "lfence\n"
+ :: [flush_pages] "r" (l1d_flush_pages),
+ [size] "r" (size)
+ : "eax", "ecx");
+}
+EXPORT_SYMBOL_GPL(flush_l1d_cache_sw);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 66d798e1a9d8..9605589bb294 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5963,8 +5963,6 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
*/
static void vmx_l1d_flush(struct kvm_vcpu *vcpu)
{
- int size = PAGE_SIZE << L1D_CACHE_ORDER;
-
/*
* This code is only executed when the the flush mode is 'cond' or
* 'always'
@@ -5993,32 +5991,13 @@ static void vmx_l1d_flush(struct kvm_vcpu *vcpu)

vcpu->stat.l1d_flush++;

- if (static_cpu_has(X86_FEATURE_FLUSH_L1D)) {
- wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH);
+ if (flush_l1d_cache_hw())
return;
- }

- asm volatile(
- /* First ensure the pages are in the TLB */
- "xorl %%eax, %%eax\n"
- ".Lpopulate_tlb:\n\t"
- "movzbl (%[flush_pages], %%" _ASM_AX "), %%ecx\n\t"
- "addl $4096, %%eax\n\t"
- "cmpl %%eax, %[size]\n\t"
- "jne .Lpopulate_tlb\n\t"
- "xorl %%eax, %%eax\n\t"
- "cpuid\n\t"
- /* Now fill the cache */
- "xorl %%eax, %%eax\n"
- ".Lfill_cache:\n"
- "movzbl (%[flush_pages], %%" _ASM_AX "), %%ecx\n\t"
- "addl $64, %%eax\n\t"
- "cmpl %%eax, %[size]\n\t"
- "jne .Lfill_cache\n\t"
- "lfence\n"
- :: [flush_pages] "r" (vmx_l1d_flush_pages),
- [size] "r" (size)
- : "eax", "ebx", "ecx", "edx");
+ preempt_disable();
+ populate_tlb_with_flush_pages(vmx_l1d_flush_pages);
+ flush_l1d_cache_sw(vmx_l1d_flush_pages);
+ preempt_enable();
}

static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr)
--
2.17.1