linux-kernel - [PATCH 3/6] x86/tdx: Support vmalloc() for tdx_enc_status

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Message-Id: <20221121195151.21812-4-decui@microsoft.com>
Date:   Mon, 21 Nov 2022 11:51:48 -0800
From:   Dexuan Cui <decui@...rosoft.com>
To:     ak@...ux.intel.com, arnd@...db.de, bp@...en8.de,
        brijesh.singh@....com, dan.j.williams@...el.com,
        dave.hansen@...ux.intel.com, haiyangz@...rosoft.com, hpa@...or.com,
        jane.chu@...cle.com, kirill.shutemov@...ux.intel.com,
        kys@...rosoft.com, linux-arch@...r.kernel.org,
        linux-hyperv@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
        peterz@...radead.org, rostedt@...dmis.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, seanjc@...gle.com,
        tglx@...utronix.de, tony.luck@...el.com, wei.liu@...nel.org,
        x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH 3/6] x86/tdx: Support vmalloc() for tdx_enc_status_changed()

When a TDX guest runs on Hyper-V, the hv_netvsc driver's netvsc_init_buf()
allocates buffers using vzalloc(), and needs to share the buffers with the
host OS by calling set_memory_decrypted(), which is not working for
vmalloc() yet. Add the support by handling the pages one by one.

Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---
 arch/x86/coco/tdx/tdx.c | 45 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 46971cc7d006..8bccae962b6d 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -5,6 +5,7 @@
 #define pr_fmt(fmt)     "tdx: " fmt
 
 #include <linux/cpufeature.h>
+#include <linux/mm.h>
 #include <asm/coco.h>
 #include <asm/tdx.h>
 #include <asm/vmx.h>
@@ -754,7 +755,8 @@ static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
  * the VMM or private to the guest.  The VMM is expected to change its mapping
  * of the page in response.
  */
-static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
+static bool tdx_enc_status_changed_for_contiguous_pages(unsigned long vaddr,
+							int numpages, bool enc)
 {
 	phys_addr_t start = __pa(vaddr);
 	phys_addr_t end   = __pa(vaddr + numpages * PAGE_SIZE);
@@ -798,6 +800,47 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
 	return true;
 }
 
+static bool tdx_enc_status_changed_for_vmalloc(unsigned long vaddr,
+					       int numpages, bool enc)
+{
+	void *start_va = (void *)vaddr;
+	void *end_va = start_va + numpages * PAGE_SIZE;
+	phys_addr_t pa;
+
+	if (offset_in_page(vaddr) != 0)
+		return false;
+
+	while (start_va < end_va) {
+		pa = slow_virt_to_phys(start_va);
+		if (!enc)
+			pa |= cc_mkdec(0);
+
+		if (!tdx_map_gpa(pa, pa + PAGE_SIZE, enc))
+			return false;
+
+		/*
+		 * private->shared conversion requires only MapGPA call.
+		 *
+		 * For shared->private conversion, accept the page using
+		 * TDX_ACCEPT_PAGE TDX module call.
+		 */
+		if (enc && !try_accept_one(&pa, PAGE_SIZE, PG_LEVEL_4K))
+			return false;
+
+		start_va += PAGE_SIZE;
+	}
+
+	return true;
+}
+
+static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
+{
+	if (is_vmalloc_addr((void *)vaddr))
+		return tdx_enc_status_changed_for_vmalloc(vaddr, numpages, enc);
+
+	return tdx_enc_status_changed_for_contiguous_pages(vaddr, numpages, enc);
+}
+
 void __init tdx_early_init(void)
 {
 	u64 cc_mask;
-- 
2.25.1