linux-kernel - [RFC PATCH V6 11/14] drivers: hv: Decrypt percpu hvcall input arg page in sev-snp enlightened guest

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Message-Id: <20230515165917.1306922-12-ltykernel@gmail.com>
Date:   Mon, 15 May 2023 12:59:13 -0400
From:   Tianyu Lan <ltykernel@...il.com>
To:     luto@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, seanjc@...gle.com, pbonzini@...hat.com,
        jgross@...e.com, tiala@...rosoft.com, kirill@...temov.name,
        jiangshan.ljs@...group.com, peterz@...radead.org,
        ashish.kalra@....com, srutherford@...gle.com,
        akpm@...ux-foundation.org, anshuman.khandual@....com,
        pawan.kumar.gupta@...ux.intel.com, adrian.hunter@...el.com,
        daniel.sneddon@...ux.intel.com, alexander.shishkin@...ux.intel.com,
        sandipan.das@....com, ray.huang@....com, brijesh.singh@....com,
        michael.roth@....com, thomas.lendacky@....com,
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Cc:     pangupta@....com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: [RFC PATCH V6 11/14] drivers: hv: Decrypt percpu hvcall input arg page in sev-snp enlightened guest

From: Tianyu Lan <tiala@...rosoft.com>

Hypervisor needs to access iput arg page and guest should decrypt
the page.

Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
---
Change since RFC V4:
        * Use pgcount to free intput arg page

Change since RFC V3:
	* Use pgcount to decrypt memory.

Change since RFC V2:
	* Set inputarg to be zero after kfree()
	* Not free mem when fail to encrypt mem in the hv_common_cpu_die().
---
 drivers/hv/hv_common.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 179bc5f5bf52..15d3054f3440 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>
 
@@ -359,6 +360,7 @@ int hv_common_cpu_init(unsigned int cpu)
 	u64 msr_vp_index;
 	gfp_t flags;
 	int pgcount = hv_root_partition ? 2 : 1;
+	int ret;
 
 	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
 	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
@@ -368,6 +370,17 @@ int hv_common_cpu_init(unsigned int cpu)
 	if (!(*inputarg))
 		return -ENOMEM;
 
+	if (hv_isolation_type_en_snp()) {
+		ret = set_memory_decrypted((unsigned long)*inputarg, pgcount);
+		if (ret) {
+			kfree(*inputarg);
+			*inputarg = NULL;
+			return ret;
+		}
+
+		memset(*inputarg, 0x00, pgcount * PAGE_SIZE);
+	}
+
 	if (hv_root_partition) {
 		outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
 		*outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
@@ -387,6 +400,7 @@ int hv_common_cpu_die(unsigned int cpu)
 {
 	unsigned long flags;
 	void **inputarg, **outputarg;
+	int pgcount = hv_root_partition ? 2 : 1;
 	void *mem;
 
 	local_irq_save(flags);
@@ -402,7 +416,12 @@ int hv_common_cpu_die(unsigned int cpu)
 
 	local_irq_restore(flags);
 
-	kfree(mem);
+	if (hv_isolation_type_en_snp()) {
+		if (!set_memory_encrypted((unsigned long)mem, pgcount))
+			kfree(mem);
+	} else {
+		kfree(mem);
+	}
 
 	return 0;
 }
-- 
2.25.1