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Date: Mon, 24 Feb 2020 16:50:43 +0100
From: Andrew Jones <drjones@...hat.com>
To: John Andersen <john.s.andersen@...el.com>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
pbonzini@...hat.com, hpa@...or.com,
sean.j.christopherson@...el.com, vkuznets@...hat.com,
wanpengli@...cent.com, jmattson@...gle.com, liran.alon@...cle.com,
luto@...nel.org, joro@...tes.org, rick.p.edgecombe@...el.com,
kristen@...ux.intel.com, arjan@...ux.intel.com,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [RFC v2 3/4] selftests: kvm: add test for CR pinning with SMM
On Tue, Feb 18, 2020 at 01:59:01PM -0800, John Andersen wrote:
> Check that paravirtualized control register pinning blocks modifications
> of pinned CR values stored in SMRAM on exit from SMM.
>
> Signed-off-by: John Andersen <john.s.andersen@...el.com>
> ---
> tools/testing/selftests/kvm/.gitignore | 1 +
> tools/testing/selftests/kvm/Makefile | 1 +
> .../selftests/kvm/include/x86_64/processor.h | 9 +
> .../selftests/kvm/x86_64/smm_cr_pin_test.c | 180 ++++++++++++++++++
> 4 files changed, 191 insertions(+)
> create mode 100644 tools/testing/selftests/kvm/x86_64/smm_cr_pin_test.c
>
> diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
> index 30072c3f52fb..08e18ae1b80f 100644
> --- a/tools/testing/selftests/kvm/.gitignore
> +++ b/tools/testing/selftests/kvm/.gitignore
> @@ -7,6 +7,7 @@
> /x86_64/platform_info_test
> /x86_64/set_sregs_test
> /x86_64/smm_test
> +/x86_64/smm_cr_pin_test
> /x86_64/state_test
> /x86_64/sync_regs_test
> /x86_64/vmx_close_while_nested_test
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index d91c53b726e6..f3fdac72fc74 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -19,6 +19,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
> TEST_GEN_PROGS_x86_64 += x86_64/platform_info_test
> TEST_GEN_PROGS_x86_64 += x86_64/set_sregs_test
> TEST_GEN_PROGS_x86_64 += x86_64/smm_test
> +TEST_GEN_PROGS_x86_64 += x86_64/smm_cr_pin_test
> TEST_GEN_PROGS_x86_64 += x86_64/state_test
> TEST_GEN_PROGS_x86_64 += x86_64/sync_regs_test
> TEST_GEN_PROGS_x86_64 += x86_64/vmx_close_while_nested_test
> diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
> index 7428513a4c68..70394d2ffa5d 100644
> --- a/tools/testing/selftests/kvm/include/x86_64/processor.h
> +++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
> @@ -197,6 +197,11 @@ static inline uint64_t get_cr0(void)
> return cr0;
> }
>
> +static inline void set_cr0(uint64_t val)
> +{
> + __asm__ __volatile__("mov %0, %%cr0" : : "r" (val) : "memory");
> +}
> +
> static inline uint64_t get_cr3(void)
> {
> uint64_t cr3;
> @@ -380,4 +385,8 @@ void kvm_get_cpu_address_width(unsigned int *pa_bits, unsigned int *va_bits);
> /* VMX_EPT_VPID_CAP bits */
> #define VMX_EPT_VPID_CAP_AD_BITS (1ULL << 21)
>
> +/* KVM MSRs */
> +#define MSR_KVM_CR0_PINNED 0x4b564d08
> +#define MSR_KVM_CR4_PINNED 0x4b564d09
> +
> #endif /* SELFTEST_KVM_PROCESSOR_H */
> diff --git a/tools/testing/selftests/kvm/x86_64/smm_cr_pin_test.c b/tools/testing/selftests/kvm/x86_64/smm_cr_pin_test.c
> new file mode 100644
> index 000000000000..013983bb4ba4
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/smm_cr_pin_test.c
> @@ -0,0 +1,180 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Tests for control register pinning not being affected by SMRAM writes.
> + */
> +#define _GNU_SOURCE /* for program_invocation_short_name */
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <string.h>
> +#include <sys/ioctl.h>
> +
> +#include "test_util.h"
> +
> +#include "kvm_util.h"
> +
> +#include "processor.h"
> +
> +#define VCPU_ID 1
> +
> +#define PAGE_SIZE 4096
> +
> +#define SMRAM_SIZE 65536
> +#define SMRAM_MEMSLOT ((1 << 16) | 1)
> +#define SMRAM_PAGES (SMRAM_SIZE / PAGE_SIZE)
> +#define SMRAM_GPA 0x1000000
> +#define SMRAM_STAGE 0xfe
> +
> +#define STR(x) #x
> +#define XSTR(s) STR(s)
linux/stringify.h is in tools/
> +
> +#define SYNC_PORT 0xe
> +#define DONE 0xff
> +
> +#define CR0_PINNED X86_CR0_WP
> +#define CR4_PINNED (X86_CR4_SMAP | X86_CR4_UMIP)
> +#define CR4_ALL (CR4_PINNED | X86_CR4_SMEP)
> +
> +/*
> + * This is compiled as normal 64-bit code, however, SMI handler is executed
> + * in real-address mode. To stay simple we're limiting ourselves to a mode
> + * independent subset of asm here.
> + * SMI handler always report back fixed stage SMRAM_STAGE.
> + */
> +uint8_t smi_handler[] = {
> + 0xb0, SMRAM_STAGE, /* mov $SMRAM_STAGE, %al */
> + 0xe4, SYNC_PORT, /* in $SYNC_PORT, %al */
> + 0x0f, 0xaa, /* rsm */
> +};
> +
> +void sync_with_host(uint64_t phase)
> +{
> + asm volatile("in $" XSTR(SYNC_PORT)", %%al \n"
> + : : "a" (phase));
> +}
Any reason not to use GUEST_SYNC() ?
> +
> +void self_smi(void)
> +{
> + wrmsr(APIC_BASE_MSR + (APIC_ICR >> 4),
> + APIC_DEST_SELF | APIC_INT_ASSERT | APIC_DM_SMI);
> +}
> +
> +void guest_code(void *unused)
> +{
Why not just define guest_code as 'void guest_code(void)' ?
> + uint64_t apicbase = rdmsr(MSR_IA32_APICBASE);
> +
> + (void)unused;
> +
> + sync_with_host(1);
> +
> + wrmsr(MSR_IA32_APICBASE, apicbase | X2APIC_ENABLE);
> +
> + sync_with_host(2);
> +
> + set_cr0(get_cr0() | CR0_PINNED);
> +
> + wrmsr(MSR_KVM_CR0_PINNED, CR0_PINNED);
> +
> + sync_with_host(3);
> +
> + set_cr4(get_cr4() | CR4_PINNED);
> +
> + sync_with_host(4);
> +
> + /* Pin SMEP low */
> + wrmsr(MSR_KVM_CR4_PINNED, CR4_PINNED);
> +
> + sync_with_host(5);
> +
> + self_smi();
> +
> + sync_with_host(DONE);
GUEST_DONE() ?
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + struct kvm_regs regs;
> + struct kvm_sregs sregs;
> + struct kvm_vm *vm;
> + struct kvm_run *run;
> + struct kvm_x86_state *state;
> + int stage, stage_reported;
> + u64 *cr;
> +
> + /* Create VM */
> + vm = vm_create_default(VCPU_ID, 0, guest_code);
> +
> + vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
> +
> + run = vcpu_state(vm, VCPU_ID);
> +
> + vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, SMRAM_GPA,
> + SMRAM_MEMSLOT, SMRAM_PAGES, 0);
> + TEST_ASSERT(vm_phy_pages_alloc(vm, SMRAM_PAGES, SMRAM_GPA, SMRAM_MEMSLOT)
> + == SMRAM_GPA, "could not allocate guest physical addresses?");
> +
> + memset(addr_gpa2hva(vm, SMRAM_GPA), 0x0, SMRAM_SIZE);
> + memcpy(addr_gpa2hva(vm, SMRAM_GPA) + 0x8000, smi_handler,
> + sizeof(smi_handler));
> +
> + vcpu_set_msr(vm, VCPU_ID, MSR_IA32_SMBASE, SMRAM_GPA);
> +
> + vcpu_args_set(vm, VCPU_ID, 1, 0);
guest_code() doesn't use inputs, so why set rdi to zero?
> +
> + for (stage = 1;; stage++) {
> + _vcpu_run(vm, VCPU_ID);
> +
> + TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
> + "Stage %d: unexpected exit reason: %u (%s),\n",
> + stage, run->exit_reason,
> + exit_reason_str(run->exit_reason));
> +
> + memset(®s, 0, sizeof(regs));
> + vcpu_regs_get(vm, VCPU_ID, ®s);
> +
> + memset(&sregs, 0, sizeof(sregs));
> + vcpu_sregs_get(vm, VCPU_ID, &sregs);
> +
> + stage_reported = regs.rax & 0xff;
If you use GUEST_ASSERT() and get_ucall() then stage_reported is uc.args[1].
Why mask it with 0xff? Shouldn't the test assert if the stage is an
unexpected value?
> +
> + if (stage_reported == DONE) {
uc.cmd == UCALL_DONE
> + TEST_ASSERT((sregs.cr0 & CR0_PINNED) == CR0_PINNED,
> + "Unexpected cr0. Bits missing: %llx",
> + sregs.cr0 ^ (CR0_PINNED | sregs.cr0));
> + TEST_ASSERT((sregs.cr4 & CR4_ALL) == CR4_PINNED,
> + "Unexpected cr4. Bits missing: %llx, cr4: %llx",
> + sregs.cr4 ^ (CR4_ALL | sregs.cr4),
> + sregs.cr4);
> + goto done;
> + }
> +
> + TEST_ASSERT(stage_reported == stage ||
> + stage_reported == SMRAM_STAGE,
> + "Unexpected stage: #%x, got %x",
> + stage, stage_reported);
> +
> + /* Within SMM modify CR0/4 to not contain pinned bits. */
> + if (stage_reported == SMRAM_STAGE) {
> + cr = (u64 *)(addr_gpa2hva(vm, SMRAM_GPA + 0x8000 + 0x7f58));
> + *cr &= ~CR0_PINNED;
> +
> + cr = (u64 *)(addr_gpa2hva(vm, SMRAM_GPA + 0x8000 + 0x7f48));
> + /* Unset pinned, set one that was pinned low */
> + *cr &= ~CR4_PINNED;
> + *cr |= X86_CR4_SMEP;
> + }
> +
> + state = vcpu_save_state(vm, VCPU_ID);
> + kvm_vm_release(vm);
> + kvm_vm_restart(vm, O_RDWR);
> + vm_vcpu_add(vm, VCPU_ID);
> + vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
> + vcpu_load_state(vm, VCPU_ID, state);
> + run = vcpu_state(vm, VCPU_ID);
> + free(state);
> + }
> +
> +done:
> + kvm_vm_free(vm);
> +}
> --
> 2.21.0
>
Thanks,
drew
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