RE: [PATCH v2 6/6] Drivers: hv: vmbus: Support TDX guests

From: Michael Kelley (LINUX)
Date: Mon Dec 12 2022 - 12:02:31 EST

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From: Dexuan Cui <decui@xxxxxxxxxxxxx> Sent: Tuesday, December 6, 2022 4:33 PM
>
> Add Hyper-V specific code so that a TDX guest can run on Hyper-V:
> No need to use hv_vp_assist_page.
> Don't use the unsafe Hyper-V TSC page.
> Don't try to use HV_REGISTER_CRASH_CTL.
> Share SynIC Event/Message pages and VMBus Monitor pages with the host.
> Use pgprot_decrypted(PAGE_KERNEL_NOENC))in hv_ringbuffer_init().
>
> Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
>
> Changes in v2:
> Used a new function hv_set_memory_enc_dec_needed() in
> __set_memory_enc_pgtable().
> Added the missing set_memory_encrypted() in hv_synic_free().
>
> ---
>
> arch/x86/hyperv/hv_init.c | 19 ++++++++---
> arch/x86/hyperv/ivm.c | 5 +++
> arch/x86/kernel/cpu/mshyperv.c | 17 +++++++++-
> arch/x86/mm/pat/set_memory.c | 2 +-
> drivers/hv/connection.c | 4 ++-
> drivers/hv/hv.c | 60 +++++++++++++++++++++++++++++++++-
> drivers/hv/hv_common.c | 6 ++++
> drivers/hv/ring_buffer.c | 2 +-
> include/asm-generic/mshyperv.h | 2 ++
> 9 files changed, 108 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index c0ba53ad8b8e..8d7b63346194 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -77,7 +77,7 @@ static int hyperv_init_ghcb(void)
> static int hv_cpu_init(unsigned int cpu)
> {
> union hv_vp_assist_msr_contents msr = { 0 };
> - struct hv_vp_assist_page **hvp = &hv_vp_assist_page[cpu];
> + struct hv_vp_assist_page **hvp;
> int ret;
>
> ret = hv_common_cpu_init(cpu);
> @@ -87,6 +87,7 @@ static int hv_cpu_init(unsigned int cpu)
> if (!hv_vp_assist_page)
> return 0;
>
> + hvp = &hv_vp_assist_page[cpu];
> if (hv_root_partition) {
> /*
> * For root partition we get the hypervisor provided VP assist
> @@ -396,11 +397,21 @@ void __init hyperv_init(void)
> if (hv_common_init())
> return;
>
> - hv_vp_assist_page = kcalloc(num_possible_cpus(),
> - sizeof(*hv_vp_assist_page), GFP_KERNEL);
> + /*
> + * The VP assist page is useless to a TDX guest: the only use we
> + * would have for it is lazy EOI, which can not be used with TDX.
> + */
> + if (hv_isolation_type_tdx())
> + hv_vp_assist_page = NULL;
> + else
> + hv_vp_assist_page = kcalloc(num_possible_cpus(),
> + sizeof(*hv_vp_assist_page),
> + GFP_KERNEL);
> if (!hv_vp_assist_page) {
> ms_hyperv.hints &=
> ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
> - goto common_free;
> +
> + if (!hv_isolation_type_tdx())
> + goto common_free;
> }
>
> if (hv_isolation_type_snp()) {
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index 07e4253b5809..4398042f10d5 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -258,6 +258,11 @@ bool hv_is_isolation_supported(void)
> return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
> }
>
> +bool hv_set_memory_enc_dec_needed(void)
> +{
> + return hv_is_isolation_supported() && !hv_isolation_type_tdx();
> +}
> +
> DEFINE_STATIC_KEY_FALSE(isolation_type_snp);
>
> /*
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 941372449ff2..24569da3c1f8 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -345,8 +345,23 @@ static void __init ms_hyperv_init_platform(void)
> }
>
> if (IS_ENABLED(CONFIG_INTEL_TDX_GUEST) &&
> - hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX)
> + hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX) {
> static_branch_enable(&isolation_type_tdx);
> +
> + /*
> + * The GPAs of SynIC Event/Message pages and VMBus
> + * Moniter pages need to be added by this offset.
> + */
> + ms_hyperv.shared_gpa_boundary = cc_mkdec(0);
> +
> + /* Don't use the unsafe Hyper-V TSC page */
> + ms_hyperv.features &=
> + ~HV_MSR_REFERENCE_TSC_AVAILABLE;
> +
> + /* HV_REGISTER_CRASH_CTL is unsupported */
> + ms_hyperv.misc_features &=
> + ~HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
> + }
> }
>
> if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index 2e5a045731de..5892196f8ade 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -2120,7 +2120,7 @@ static int __set_memory_enc_pgtable(unsigned long addr,
> int numpages, bool enc)
>
> static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
> {
> - if (hv_is_isolation_supported())
> + if (hv_set_memory_enc_dec_needed())
> return hv_set_mem_host_visibility(addr, numpages, !enc);
>
> if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 9dc27e5d367a..1ecc3c29e3f7 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -250,12 +250,14 @@ int vmbus_connect(void)
> * Isolation VM with AMD SNP needs to access monitor page via
> * address space above shared gpa boundary.
> */
> - if (hv_isolation_type_snp()) {
> + if (hv_isolation_type_snp() || hv_isolation_type_tdx()) {
> vmbus_connection.monitor_pages_pa[0] +=
> ms_hyperv.shared_gpa_boundary;
> vmbus_connection.monitor_pages_pa[1] +=
> ms_hyperv.shared_gpa_boundary;
> + }
>
> + if (hv_isolation_type_snp()) {
> vmbus_connection.monitor_pages[0]
> =
> memremap(vmbus_connection.monitor_pages_pa[0],
> HV_HYP_PAGE_SIZE,
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 4d6480d57546..78aca415985c 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -18,6 +18,7 @@
> #include <linux/clockchips.h>
> #include <linux/delay.h>
> #include <linux/interrupt.h>
> +#include <linux/set_memory.h>
> #include <clocksource/hyperv_timer.h>
> #include <asm/mshyperv.h>
> #include "hyperv_vmbus.h"
> @@ -119,6 +120,7 @@ int hv_synic_alloc(void)
> {
> int cpu;
> struct hv_per_cpu_context *hv_cpu;
> + int ret = -ENOMEM;
>
> /*
> * First, zero all per-cpu memory areas so hv_synic_free() can
> @@ -168,6 +170,30 @@ int hv_synic_alloc(void)
> pr_err("Unable to allocate post msg page\n");
> goto err;
> }
> +
> +
> + if (hv_isolation_type_tdx()) {
> + ret = set_memory_decrypted(
> + (unsigned long)hv_cpu->synic_message_page, 1);
> + if (ret) {
> + pr_err("Failed to decrypt SYNIC msg page\n");
> + goto err;
> + }
> +
> + ret = set_memory_decrypted(
> + (unsigned long)hv_cpu->synic_event_page, 1);
> + if (ret) {
> + pr_err("Failed to decrypt SYNIC event page\n");
> + goto err;
> + }
> +
> + ret = set_memory_decrypted(
> + (unsigned long)hv_cpu->post_msg_page, 1);
> + if (ret) {
> + pr_err("Failed to decrypt post msg page\n");
> + goto err;
> + }
> + }
> }
>
> return 0;
> @@ -176,18 +202,42 @@ int hv_synic_alloc(void)
> * Any memory allocations that succeeded will be freed when
> * the caller cleans up by calling hv_synic_free()
> */
> - return -ENOMEM;
> + return ret;
> }
>
>
> void hv_synic_free(void)
> {
> int cpu;
> + int ret;
>
> for_each_present_cpu(cpu) {
> struct hv_per_cpu_context *hv_cpu
> = per_cpu_ptr(hv_context.cpu_context, cpu);
>
> + if (hv_isolation_type_tdx()) {
> + ret = set_memory_encrypted(
> + (unsigned long)hv_cpu->synic_message_page, 1);
> + if (ret) {
> + pr_err("Failed to encrypt SYNIC msg page\n");
> + continue;
> + }
> +
> + ret = set_memory_encrypted(
> + (unsigned long)hv_cpu->synic_event_page, 1);
> + if (ret) {
> + pr_err("Failed to encrypt SYNIC event page\n");
> + continue;
> + }
> +
> + ret = set_memory_encrypted(
> + (unsigned long)hv_cpu->post_msg_page, 1);
> + if (ret) {
> + pr_err("Failed to encrypt post msg page\n");
> + continue;
> + }
> + }
> +
> free_page((unsigned long)hv_cpu->synic_event_page);
> free_page((unsigned long)hv_cpu->synic_message_page);
> free_page((unsigned long)hv_cpu->post_msg_page);
> @@ -225,6 +275,10 @@ void hv_synic_enable_regs(unsigned int cpu)
> } else {
> simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
> >> HV_HYP_PAGE_SHIFT;
> +
> + if (hv_isolation_type_tdx())
> + simp.base_simp_gpa |= ms_hyperv.shared_gpa_boundary
> + >> HV_HYP_PAGE_SHIFT;

Since we're using cc_mkdec() in hv_do_hypercall() to set the SHARED bit,
perhaps the same could be done here to simplify the code and avoid the
explicit call to hv_isolation_type_tdx():

simp.base_simp_gpa = cc_mkdec(virt_to_phys(hv_cpu->synic_message))
>> HV_HYP_PAGE_SHIFT;

cc_mkdec() does nothing in a normal VM, and vTOM VMs are already
special-cased.

> }
>
> hv_set_register(HV_REGISTER_SIMP, simp.as_uint64);
> @@ -243,6 +297,10 @@ void hv_synic_enable_regs(unsigned int cpu)
> } else {
> siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
> >> HV_HYP_PAGE_SHIFT;
> +
> + if (hv_isolation_type_tdx())
> + siefp.base_siefp_gpa |= ms_hyperv.shared_gpa_boundary
> + >> HV_HYP_PAGE_SHIFT;

Same here.

> }
>
> hv_set_register(HV_REGISTER_SIEFP, siefp.as_uint64);
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index a9a03ab04b97..192dcf295dfc 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -262,6 +262,12 @@ bool __weak hv_is_isolation_supported(void)
> }
> EXPORT_SYMBOL_GPL(hv_is_isolation_supported);
>
> +bool __weak hv_set_memory_enc_dec_needed(void)
> +{
> + return false;
> +}
> +EXPORT_SYMBOL_GPL(hv_set_memory_enc_dec_needed);
> +
> bool __weak hv_isolation_type_snp(void)
> {
> return false;
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index c6692fd5ab15..a51da82316ce 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -233,7 +233,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
>
> ring_info->ring_buffer = (struct hv_ring_buffer *)
> vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
> - PAGE_KERNEL);
> + pgprot_decrypted(PAGE_KERNEL_NOENC));
>
> kfree(pages_wraparound);
> if (!ring_info->ring_buffer)
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index bfb9eb9d7215..b7b1b18c9854 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -262,6 +262,7 @@ bool hv_is_hyperv_initialized(void);
> bool hv_is_hibernation_supported(void);
> enum hv_isolation_type hv_get_isolation_type(void);
> bool hv_is_isolation_supported(void);
> +bool hv_set_memory_enc_dec_needed(void);
> bool hv_isolation_type_snp(void);
> u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
> void hyperv_cleanup(void);
> @@ -274,6 +275,7 @@ static inline bool hv_is_hyperv_initialized(void) { return false; }
> static inline bool hv_is_hibernation_supported(void) { return false; }
> static inline void hyperv_cleanup(void) {}
> static inline bool hv_is_isolation_supported(void) { return false; }
> +static inline bool hv_set_memory_enc_dec_needed(void) { return false; }
> static inline enum hv_isolation_type hv_get_isolation_type(void)
> {
> return HV_ISOLATION_TYPE_NONE;
> --
> 2.25.1

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