Re: [PATCH v2 06/12] x86/sev: Replace occurrences of sev_active() with prot_guest_has()

On 8/17/21 5:02 AM, Borislav Petkov wrote:

On Fri, Aug 13, 2021 at 11:59:25AM -0500, Tom Lendacky wrote:

quoted

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 8e7b517ad738..66ff788b79c9 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c

@@ -167,7 +167,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
 	}
 	pte = pte_offset_kernel(pmd, vaddr);
 
-	if (sev_active())
+	if (prot_guest_has(PATTR_GUEST_MEM_ENCRYPT))
 		prot = PAGE_KERNEL_EXEC;
 
 	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, prot));

@@ -207,7 +207,7 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
 	level4p = (pgd_t *)__va(start_pgtable);
 	clear_page(level4p);
 
-	if (sev_active()) {
+	if (prot_guest_has(PATTR_GUEST_MEM_ENCRYPT)) {
 		info.page_flag   |= _PAGE_ENC;
 		info.kernpg_flag |= _PAGE_ENC;
 	}

@@ -570,12 +570,12 @@ void arch_kexec_unprotect_crashkres(void)
  */
 int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, gfp_t gfp)
 {
-	if (sev_active())
+	if (!prot_guest_has(PATTR_HOST_MEM_ENCRYPT))
 		return 0;
 
 	/*
-	 * If SME is active we need to be sure that kexec pages are
-	 * not encrypted because when we boot to the new kernel the
+	 * If host memory encryption is active we need to be sure that kexec
+	 * pages are not encrypted because when we boot to the new kernel the
 	 * pages won't be accessed encrypted (initially).
 	 */

That hunk belongs logically into the previous patch which removes
sme_active().

I was trying to keep the sev_active() changes separate... so even though
it's an SME thing, I kept it here. But I can move it to the previous
patch, it just might look strange.

quoted

 	return set_memory_decrypted((unsigned long)vaddr, pages);

@@ -583,12 +583,12 @@ int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, gfp_t gfp)
 
 void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages)
 {
-	if (sev_active())
+	if (!prot_guest_has(PATTR_HOST_MEM_ENCRYPT))
 		return;
 
 	/*
-	 * If SME is active we need to reset the pages back to being
-	 * an encrypted mapping before freeing them.
+	 * If host memory encryption is active we need to reset the pages back
+	 * to being an encrypted mapping before freeing them.
 	 */
 	set_memory_encrypted((unsigned long)vaddr, pages);
 }

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e8ccab50ebf6..b69f5ac622d5 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c

@@ -25,6 +25,7 @@
 #include <linux/pagemap.h>
 #include <linux/swap.h>
 #include <linux/rwsem.h>
+#include <linux/protected_guest.h>
 
 #include <asm/apic.h>
 #include <asm/perf_event.h>

@@ -457,7 +458,7 @@ static int has_svm(void)
 		return 0;
 	}
 
-	if (sev_active()) {
+	if (prot_guest_has(PATTR_SEV)) {
 		pr_info("KVM is unsupported when running as an SEV guest\n");
 		return 0;

Same question as for PATTR_SME. PATTR_GUEST_MEM_ENCRYPT should be enough.

Yup, I'll change them all.

quoted

@@ -373,7 +373,7 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
  * up under SME the trampoline area cannot be encrypted, whereas under SEV
  * the trampoline area must be encrypted.
  */
-bool sev_active(void)
+static bool sev_active(void)
 {
 	return sev_status & MSR_AMD64_SEV_ENABLED;
 }

@@ -382,7 +382,6 @@ static bool sme_active(void)
 {
 	return sme_me_mask && !sev_active();
 }
-EXPORT_SYMBOL_GPL(sev_active);

Just get rid of it altogether.

Ok.

Thanks,
Tom

Thx.