[RFC PATCH 07/15] x86/virt/tdx: Prepare Quote buffer during extension bringup

[Xu Yilun]

From: Peter Fang <peter.fang@xxxxxxxxx>

The host uses a Quote buffer to communicate with the TDX module when
generating Quotes. Because the Quote buffer is shared with TDX guests,
prepare the required metadata during Quoting extension bringup.

This mostly involves determining the physical addresses of the Quote
buffer pages and arranging them in the HPA_LINKED_LIST format defined by
the Intel TDX Module ABI specification.

Signed-off-by: Peter Fang <peter.fang@xxxxxxxxx>
Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/virt/vmx/tdx/tdx.c | 85 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 84 insertions(+), 1 deletion(-)

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index fb84fb6d952b..9d04293394d7 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -32,6 +32,7 @@
 #include <linux/idr.h>
 #include <linux/kvm_types.h>
 #include <linux/bitfield.h>
+#include <linux/vmalloc.h>
 #include <asm/page.h>
 #include <asm/special_insns.h>
 #include <asm/msr-index.h>
@@ -61,6 +62,13 @@ static LIST_HEAD(tdx_memlist);
 static struct tdx_sys_info tdx_sysinfo __ro_after_init;
 static bool tdx_module_initialized __ro_after_init;
 
+static struct quote_data {
+	void *buf;
+	u64 buf_len;
+	u64 *hpa_list;
+	phys_addr_t hpa_list_pa;
+} quote_data;
+
 typedef void (*sc_err_func_t)(u64 fn, u64 err, struct tdx_module_args *args);
 
 static inline void seamcall_err(u64 fn, u64 err, struct tdx_module_args *args)
@@ -1205,9 +1213,78 @@ static inline u64 tdx_tdr_pa(struct tdx_td *td)
 	return page_to_phys(td->tdr_page);
 }
 
+#define HPAS_PER_PAGE			(PAGE_SIZE / sizeof(u64))
+
+static int tdx_quote_create_buf(unsigned int nr_pages, struct quote_data *qdata)
+{
+	unsigned long pfn;
+	u64 qlist_npages;
+	int err, i, j;
+	u64 *qlist;
+	void *qbuf;
+
+	if (!nr_pages)
+		return -EINVAL;
+
+	/* The last entry of a linked list page points to the next page	*/
+	qlist_npages = (u64)DIV_ROUND_UP(nr_pages, HPAS_PER_PAGE - 1);
+
+	qlist = vmalloc_array(qlist_npages, PAGE_SIZE);
+	if (!qlist) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+
+	/*
+	 * Make sure unfilled entries are always -1, which means NULL in TDX.
+	 * Only the last page needs to be filled. All the other pages will be
+	 * fully populated.
+	 */
+	memset((u8 *)qlist + (qlist_npages - 1) * PAGE_SIZE, 0xff, PAGE_SIZE);
+
+	qbuf = vcalloc(nr_pages, PAGE_SIZE);
+	if (!qbuf) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+
+	/* Populate HPA_LINKED_LIST as per TDX ABI spec */
+	for (i = 0, j = 0; j < nr_pages; i++) {
+		if ((i % HPAS_PER_PAGE) == HPAS_PER_PAGE - 1) {
+			/*
+			 * The last entry always points to the next page. The
+			 * address of the following entry must be on next page's
+			 * boundary.
+			 */
+			pfn = vmalloc_to_pfn(&qlist[i + 1]);
+			qlist[i] = PFN_PHYS(pfn);
+			continue;
+		}
+
+		pfn = vmalloc_to_pfn((u8 *)qbuf + j * PAGE_SIZE);
+		qlist[i] = PFN_PHYS(pfn);
+		j++;
+	}
+
+	qdata->buf = qbuf;
+	qdata->buf_len = (u64)nr_pages * PAGE_SIZE;
+	qdata->hpa_list = qlist;
+
+	pfn = vmalloc_to_pfn(qlist);
+	qdata->hpa_list_pa = PFN_PHYS(pfn);
+
+	return 0;
+
+out_err:
+	vfree(qlist);
+
+	return err;
+}
+
 static void tdx_quote_init(void)
 {
 	struct tdx_module_args args = {};
+	unsigned int nr_quote_pages;
 	u64 r;
 
 	do {
@@ -1218,7 +1295,13 @@ static void tdx_quote_init(void)
 		return;
 
 	/* Quoting metadata is valid only after initialization */
-	get_tdx_sys_info_quote(&tdx_sysinfo.quote);
+	if (get_tdx_sys_info_quote(&tdx_sysinfo.quote))
+		return;
+
+	nr_quote_pages = PAGE_ALIGN(tdx_sysinfo.quote.max_quote_size) /
+			 PAGE_SIZE;
+	if (tdx_quote_create_buf(nr_quote_pages, &quote_data))
+		pr_err("Failed to create quote buffer\n");
 }
 
 /* Initialize the TDX Module Extensions then Extension-SEAMCALLs can be used */
-- 
2.25.1