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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     Tianyu Lan <ltykernel@gmail.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "x86@kernel.org" <x86@kernel.org>, "hpa@zytor.com" <hpa@zytor.com>,
        "daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
        "arnd@arndb.de" <arnd@arndb.de>
CC:     Tianyu Lan <Tianyu.Lan@microsoft.com>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>
Subject: RE: [PATCH V2 4/9] drivers: hv: Mark percpu hvcall input arg page
 unencrypted in SEV-SNP enlightened guest
Thread-Topic: [PATCH V2 4/9] drivers: hv: Mark percpu hvcall input arg page
 unencrypted in SEV-SNP enlightened guest
Thread-Index: AQHZqKawEswy81hKaEC9zSZS+zSGUK+ps5nw
Date:   Tue, 4 Jul 2023 14:19:32 +0000
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References: <20230627032248.2170007-1-ltykernel@gmail.com>
 <20230627032248.2170007-5-ltykernel@gmail.com>
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From: Tianyu Lan <ltykernel@gmail.com> Sent: Monday, June 26, 2023 8:23 PM
>=20
> Hypervisor needs to access input arg, VMBus synic event and
> message pages. Mark these pages unencrypted in the SEV-SNP
> guest and free them only if they have been marked encrypted
> successfully.
>=20
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
>  drivers/hv/hv.c        | 57 +++++++++++++++++++++++++++++++++++++++---
>  drivers/hv/hv_common.c | 13 ++++++++++
>  2 files changed, 67 insertions(+), 3 deletions(-)
>=20
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index de6708dbe0df..ec6e35a0d9bf 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -20,6 +20,7 @@
>  #include <linux/interrupt.h>
>  #include <clocksource/hyperv_timer.h>
>  #include <asm/mshyperv.h>
> +#include <linux/set_memory.h>
>  #include "hyperv_vmbus.h"
>=20
>  /* The one and only */
> @@ -78,7 +79,7 @@ int hv_post_message(union hv_connection_id connection_i=
d,
>=20
>  int hv_synic_alloc(void)
>  {
> -	int cpu;
> +	int cpu, ret =3D -ENOMEM;
>  	struct hv_per_cpu_context *hv_cpu;
>=20
>  	/*
> @@ -123,26 +124,76 @@ int hv_synic_alloc(void)
>  				goto err;
>  			}
>  		}
> +
> +		if (hv_isolation_type_en_snp()) {
> +			ret =3D set_memory_decrypted((unsigned long)
> +				hv_cpu->synic_message_page, 1);
> +			if (ret) {
> +				pr_err("Failed to decrypt SYNIC msg page: %d\n", ret);
> +				hv_cpu->synic_message_page =3D NULL;
> +
> +				/*
> +				 * Free the event page here so that hv_synic_free()
> +				 * won't later try to re-encrypt it.
> +				 */
> +				free_page((unsigned long)hv_cpu->synic_event_page);
> +				hv_cpu->synic_event_page =3D NULL;
> +				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: %d\n", ret);
> +				hv_cpu->synic_event_page =3D NULL;
> +				goto err;
> +			}
> +
> +			memset(hv_cpu->synic_message_page, 0, PAGE_SIZE);
> +			memset(hv_cpu->synic_event_page, 0, PAGE_SIZE);
> +		}
>  	}
>=20
>  	return 0;
> +
>  err:
>  	/*
>  	 * 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 cpu, ret;
>=20
>  	for_each_present_cpu(cpu) {
>  		struct hv_per_cpu_context *hv_cpu
>  			=3D per_cpu_ptr(hv_context.cpu_context, cpu);
>=20
> +		/* It's better to leak the page if the encryption fails. */
> +		if (hv_isolation_type_en_snp()) {
> +			if (hv_cpu->synic_message_page) {
> +				ret =3D set_memory_encrypted((unsigned long)
> +					hv_cpu->synic_message_page, 1);
> +				if (ret) {
> +					pr_err("Failed to encrypt SYNIC msg page: %d\n", ret);
> +					hv_cpu->synic_message_page =3D NULL;
> +				}
> +			}
> +
> +			if (hv_cpu->synic_event_page) {
> +				ret =3D set_memory_encrypted((unsigned long)
> +					hv_cpu->synic_event_page, 1);
> +				if (ret) {
> +					pr_err("Failed to encrypt SYNIC event page: %d\n", ret);
> +					hv_cpu->synic_event_page =3D NULL;
> +				}
> +			}
> +		}
> +
>  		free_page((unsigned long)hv_cpu->synic_event_page);
>  		free_page((unsigned long)hv_cpu->synic_message_page);
>  	}
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 4b4aa53c34c2..2d43ba2bc925 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -24,6 +24,7 @@
>  #include <linux/kmsg_dump.h>
>  #include <linux/slab.h>
>  #include <linux/dma-map-ops.h>
> +#include <linux/set_memory.h>
>  #include <asm/hyperv-tlfs.h>
>  #include <asm/mshyperv.h>
>=20
> @@ -359,6 +360,7 @@ int hv_common_cpu_init(unsigned int cpu)
>  	u64 msr_vp_index;
>  	gfp_t flags;
>  	int pgcount =3D hv_root_partition ? 2 : 1;
> +	int ret;
>=20
>  	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
>  	flags =3D irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
> @@ -378,6 +380,17 @@ int hv_common_cpu_init(unsigned int cpu)
>  			outputarg =3D (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
>  			*outputarg =3D (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
>  		}
> +
> +		if (hv_isolation_type_en_snp()) {
> +			ret =3D set_memory_decrypted((unsigned long)*inputarg, pgcount);
> +			if (ret) {
> +				kfree(*inputarg);
> +				*inputarg =3D NULL;
> +				return ret;
> +			}
> +
> +			memset(*inputarg, 0x00, pgcount * PAGE_SIZE);
> +		}
>  	}
>=20
>  	msr_vp_index =3D hv_get_register(HV_REGISTER_VP_INDEX);
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>