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CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2 6/6] Drivers: hv: vmbus: Support TDX guests
Thread-Topic: [PATCH v2 6/6] Drivers: hv: vmbus: Support TDX guests
Thread-Index: AQHZCdO7v/iQZOay70+ESepxHwMb165qgFMQ
Date:   Mon, 12 Dec 2022 17:02:16 +0000
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References: <20221207003325.21503-1-decui@microsoft.com>
 <20221207003325.21503-7-decui@microsoft.com>
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From: Dexuan Cui <decui@microsoft.com> Sent: Tuesday, December 6, 2022 4:33=
 PM
>=20
> 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().
>=20
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
>=20
> 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().
>=20
> ---
>=20
>  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(-)
>=20
> 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 =3D { 0 };
> -	struct hv_vp_assist_page **hvp =3D &hv_vp_assist_page[cpu];
> +	struct hv_vp_assist_page **hvp;
>  	int ret;
>=20
>  	ret =3D hv_common_cpu_init(cpu);
> @@ -87,6 +87,7 @@ static int hv_cpu_init(unsigned int cpu)
>  	if (!hv_vp_assist_page)
>  		return 0;
>=20
> +	hvp =3D &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;
>=20
> -	hv_vp_assist_page =3D 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 =3D NULL;
> +	else
> +		hv_vp_assist_page =3D kcalloc(num_possible_cpus(),
> +					    sizeof(*hv_vp_assist_page),
> +					    GFP_KERNEL);
>  	if (!hv_vp_assist_page) {
>  		ms_hyperv.hints &=3D
> ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
> -		goto common_free;
> +
> +		if (!hv_isolation_type_tdx())
> +			goto common_free;
>  	}
>=20
>  	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() !=3D HV_ISOLATION_TYPE_NONE;
>  }
>=20
> +bool hv_set_memory_enc_dec_needed(void)
> +{
> +	return hv_is_isolation_supported() && !hv_isolation_type_tdx();
> +}
> +
>  DEFINE_STATIC_KEY_FALSE(isolation_type_snp);
>=20
>  /*
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyper=
v.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)
>  		}
>=20
>  		if (IS_ENABLED(CONFIG_INTEL_TDX_GUEST) &&
> -		    hv_get_isolation_type() =3D=3D HV_ISOLATION_TYPE_TDX)
> +		    hv_get_isolation_type() =3D=3D 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 =3D cc_mkdec(0);
> +
> +			/* Don't use the unsafe Hyper-V TSC page */
> +			ms_hyperv.features &=3D
> +				~HV_MSR_REFERENCE_TSC_AVAILABLE;
> +
> +			/* HV_REGISTER_CRASH_CTL is unsupported */
> +			ms_hyperv.misc_features &=3D
> +				 ~HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
> +		}
>  	}
>=20
>  	if (hv_max_functions_eax >=3D 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 a=
ddr,
> int numpages, bool enc)
>=20
>  static int __set_memory_enc_dec(unsigned long addr, int numpages, bool e=
nc)
>  {
> -	if (hv_is_isolation_supported())
> +	if (hv_set_memory_enc_dec_needed())
>  		return hv_set_mem_host_visibility(addr, numpages, !enc);
>=20
>  	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] +=3D
>  				ms_hyperv.shared_gpa_boundary;
>  			vmbus_connection.monitor_pages_pa[1] +=3D
>  				ms_hyperv.shared_gpa_boundary;
> +		}
>=20
> +		if (hv_isolation_type_snp()) {
>  			vmbus_connection.monitor_pages[0]
>  				=3D
> 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 =3D -ENOMEM;
>=20
>  	/*
>  	 * 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 =3D 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 =3D 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 =3D set_memory_decrypted(
> +				(unsigned long)hv_cpu->post_msg_page, 1);
> +			if (ret) {
> +				pr_err("Failed to decrypt post msg page\n");
> +				goto err;
> +			}
> +		}
>  	}
>=20
>  	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;
>  }
>=20
>=20
>  void hv_synic_free(void)
>  {
>  	int cpu;
> +	int ret;
>=20
>  	for_each_present_cpu(cpu) {
>  		struct hv_per_cpu_context *hv_cpu
>  			=3D per_cpu_ptr(hv_context.cpu_context, cpu);
>=20
> +		if (hv_isolation_type_tdx()) {
> +			ret =3D set_memory_encrypted(
> +				(unsigned long)hv_cpu->synic_message_page, 1);
> +			if (ret) {
> +				pr_err("Failed to encrypt SYNIC msg page\n");
> +				continue;
> +			}
> +
> +			ret =3D set_memory_encrypted(
> +				(unsigned long)hv_cpu->synic_event_page, 1);
> +			if (ret) {
> +				pr_err("Failed to encrypt SYNIC event page\n");
> +				continue;
> +			}
> +
> +			ret =3D 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 =3D virt_to_phys(hv_cpu->synic_message_page)
>  			>> HV_HYP_PAGE_SHIFT;
> +
> +		if (hv_isolation_type_tdx())
> +			simp.base_simp_gpa |=3D 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 =3D 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.

>  	}
>=20
>  	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 =3D virt_to_phys(hv_cpu->synic_event_page)
>  			>> HV_HYP_PAGE_SHIFT;
> +
> +		if (hv_isolation_type_tdx())
> +			siefp.base_siefp_gpa |=3D ms_hyperv.shared_gpa_boundary
> +				>> HV_HYP_PAGE_SHIFT;

Same here.


>  	}
>=20
>  	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);
>=20
> +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 *ri=
ng_info,
>=20
>  		ring_info->ring_buffer =3D (struct hv_ring_buffer *)
>  			vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
> -				PAGE_KERNEL);
> +				pgprot_decrypted(PAGE_KERNEL_NOENC));
>=20
>  		kfree(pages_wraparound);
>  		if (!ring_info->ring_buffer)
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyper=
v.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) { r=
eturn 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