x86/sev: Use the SVSM to create a vCPU when not in VMPL0

Using the RMPADJUST instruction, the VMSA attribute can only be changed
at VMPL0. An SVSM will be present when running at VMPL1 or a lower
privilege level.

In that case, use the SVSM_CORE_CREATE_VCPU call or the
SVSM_CORE_DESTROY_VCPU call to perform VMSA attribute changes. Use the
VMPL level supplied by the SVSM for the VMSA when starting the AP.

  [ bp: Fix typo + touchups. ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/bcdd95ecabe9723673b9693c7f1533a2b8f17781.1717600736.git.thomas.lendacky@amd.com

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 874295a8c23bfd1c21dcd739189adc51235348ac..1d0b1b23fafbabe99944cd3963ba82adb84ed02a 100644 (file)
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -233,6 +233,8 @@ struct svsm_call {
 #define SVSM_CORE_CALL(x)              ((0ULL << 32) | (x))
 #define SVSM_CORE_REMAP_CA             0
 #define SVSM_CORE_PVALIDATE            1
+#define SVSM_CORE_CREATE_VCPU          2
+#define SVSM_CORE_DELETE_VCPU          3
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 extern void __sev_es_ist_enter(struct pt_regs *regs);

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index f1d11e723f6614b37bbcffb2233e475c32873e4f..2586ba66257294a2c9e112927f869ac393afcc70 100644 (file)
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1010,22 +1010,49 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end)
        set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
 }
 
-static int snp_set_vmsa(void *va, bool vmsa)
+static int snp_set_vmsa(void *va, void *caa, int apic_id, bool make_vmsa)
 {
-       u64 attrs;
+       int ret;
 
-       /*
-        * Running at VMPL0 allows the kernel to change the VMSA bit for a page
-        * using the RMPADJUST instruction. However, for the instruction to
-        * succeed it must target the permissions of a lesser privileged
-        * (higher numbered) VMPL level, so use VMPL1 (refer to the RMPADJUST
-        * instruction in the AMD64 APM Volume 3).
-        */
-       attrs = 1;
-       if (vmsa)
-               attrs |= RMPADJUST_VMSA_PAGE_BIT;
+       if (snp_vmpl) {
+               struct svsm_call call = {};
+               unsigned long flags;
+
+               local_irq_save(flags);
+
+               call.caa = this_cpu_read(svsm_caa);
+               call.rcx = __pa(va);
+
+               if (make_vmsa) {
+                       /* Protocol 0, Call ID 2 */
+                       call.rax = SVSM_CORE_CALL(SVSM_CORE_CREATE_VCPU);
+                       call.rdx = __pa(caa);
+                       call.r8  = apic_id;
+               } else {
+                       /* Protocol 0, Call ID 3 */
+                       call.rax = SVSM_CORE_CALL(SVSM_CORE_DELETE_VCPU);
+               }
 
-       return rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
+               ret = svsm_perform_call_protocol(&call);
+
+               local_irq_restore(flags);
+       } else {
+               /*
+                * If the kernel runs at VMPL0, it can change the VMSA
+                * bit for a page using the RMPADJUST instruction.
+                * However, for the instruction to succeed it must
+                * target the permissions of a lesser privileged (higher
+                * numbered) VMPL level, so use VMPL1.
+                */
+               u64 attrs = 1;
+
+               if (make_vmsa)
+                       attrs |= RMPADJUST_VMSA_PAGE_BIT;
+
+               ret = rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
+       }
+
+       return ret;
 }
 
 #define __ATTR_BASE            (SVM_SELECTOR_P_MASK | SVM_SELECTOR_S_MASK)
@@ -1059,11 +1086,11 @@ static void *snp_alloc_vmsa_page(int cpu)
        return page_address(p + 1);
 }
 
-static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa)
+static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa, int apic_id)
 {
        int err;
 
-       err = snp_set_vmsa(vmsa, false);
+       err = snp_set_vmsa(vmsa, NULL, apic_id, false);
        if (err)
                pr_err("clear VMSA page failed (%u), leaking page\n", err);
        else
@@ -1074,6 +1101,7 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
 {
        struct sev_es_save_area *cur_vmsa, *vmsa;
        struct ghcb_state state;
+       struct svsm_ca *caa;
        unsigned long flags;
        struct ghcb *ghcb;
        u8 sipi_vector;
@@ -1120,6 +1148,9 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
        if (!vmsa)
                return -ENOMEM;
 
+       /* If an SVSM is present, the SVSM per-CPU CAA will be !NULL */
+       caa = per_cpu(svsm_caa, cpu);
+
        /* CR4 should maintain the MCE value */
        cr4 = native_read_cr4() & X86_CR4_MCE;
 
@@ -1167,11 +1198,11 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
         *   VMPL level
         *   SEV_FEATURES (matches the SEV STATUS MSR right shifted 2 bits)
         */
-       vmsa->vmpl              = 0;
+       vmsa->vmpl              = snp_vmpl;
        vmsa->sev_features      = sev_status >> 2;
 
        /* Switch the page over to a VMSA page now that it is initialized */
-       ret = snp_set_vmsa(vmsa, true);
+       ret = snp_set_vmsa(vmsa, caa, apic_id, true);
        if (ret) {
                pr_err("set VMSA page failed (%u)\n", ret);
                free_page((unsigned long)vmsa);
@@ -1187,7 +1218,10 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
        vc_ghcb_invalidate(ghcb);
        ghcb_set_rax(ghcb, vmsa->sev_features);
        ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_CREATION);
-       ghcb_set_sw_exit_info_1(ghcb, ((u64)apic_id << 32) | SVM_VMGEXIT_AP_CREATE);
+       ghcb_set_sw_exit_info_1(ghcb,
+                               ((u64)apic_id << 32)    |
+                               ((u64)snp_vmpl << 16)   |
+                               SVM_VMGEXIT_AP_CREATE);
        ghcb_set_sw_exit_info_2(ghcb, __pa(vmsa));
 
        sev_es_wr_ghcb_msr(__pa(ghcb));
@@ -1205,13 +1239,13 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
 
        /* Perform cleanup if there was an error */
        if (ret) {
-               snp_cleanup_vmsa(vmsa);
+               snp_cleanup_vmsa(vmsa, apic_id);
                vmsa = NULL;
        }
 
        /* Free up any previous VMSA page */
        if (cur_vmsa)
-               snp_cleanup_vmsa(cur_vmsa);
+               snp_cleanup_vmsa(cur_vmsa, apic_id);
 
        /* Record the current VMSA page */
        per_cpu(sev_vmsa, cpu) = vmsa;