linux-kernel - [RFC PATCH v2 02/35] Add arch specific additional guest pages

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Message-ID: <20250923050942.206116-3-Neeraj.Upadhyay@amd.com>
Date: Tue, 23 Sep 2025 10:39:09 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: <kvm@...r.kernel.org>, <seanjc@...gle.com>, <pbonzini@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <Thomas.Lendacky@....com>,
	<nikunj@....com>, <Santosh.Shukla@....com>, <Vasant.Hegde@....com>,
	<Suravee.Suthikulpanit@....com>, <bp@...en8.de>, <David.Kaplan@....com>,
	<huibo.wang@....com>, <naveen.rao@....com>, <pgonda@...gle.com>,
	<linux-kselftest@...r.kernel.org>, <shuah@...nel.org>, <tiala@...rosoft.com>
Subject: [RFC PATCH v2 02/35] Add arch specific additional guest pages

From: Peter Gonda <pgonda@...gle.com>

SEV-ES guests need additional pages allocated for their GHCBs. Add arch
specific function definition with __weak to allow for overriding for X86
specific SEV-ES functionality.

Cc: Vishal Annapurve <vannapurve@...gle.com>
Cc: Ackerley Tng <ackerleytng@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Carlos Bilbao <carlos.bilbao@....com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Michael Roth <michael.roth@....com>
Cc: kvm@...r.kernel.org
Cc: linux-kselftest@...r.kernel.org
Signed-off-by: Peter Gonda <pgonda@...gle.com>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
---
 tools/testing/selftests/kvm/include/kvm_util.h |  2 ++
 tools/testing/selftests/kvm/lib/kvm_util.c     | 16 ++++++++++++----
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 23a506d7eca3..1a9764658eb9 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -268,6 +268,8 @@ int get_kvm_param_integer(const char *param);
 int get_kvm_intel_param_integer(const char *param);
 int get_kvm_amd_param_integer(const char *param);
 
+int kvm_arch_vm_additional_pages_required(struct vm_shape shape,
+                                         uint64_t page_size);
 unsigned int kvm_check_cap(long cap);
 
 static inline bool kvm_has_cap(long cap)
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index c3f5142b0a54..a3b16793b2fd 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -391,11 +391,11 @@ struct kvm_vm *____vm_create(struct vm_shape shape)
 	return vm;
 }
 
-static uint64_t vm_nr_pages_required(enum vm_guest_mode mode,
+static uint64_t vm_nr_pages_required(struct vm_shape shape,
 				     uint32_t nr_runnable_vcpus,
 				     uint64_t extra_mem_pages)
 {
-	uint64_t page_size = vm_guest_mode_params[mode].page_size;
+	uint64_t page_size = vm_guest_mode_params[shape.mode].page_size;
 	uint64_t nr_pages;
 
 	TEST_ASSERT(nr_runnable_vcpus,
@@ -427,7 +427,9 @@ static uint64_t vm_nr_pages_required(enum vm_guest_mode mode,
 	/* Account for the number of pages needed by ucall. */
 	nr_pages += ucall_nr_pages_required(page_size);
 
-	return vm_adjust_num_guest_pages(mode, nr_pages);
+	nr_pages += kvm_arch_vm_additional_pages_required(shape, page_size);
+
+	return vm_adjust_num_guest_pages(shape.mode, nr_pages);
 }
 
 void kvm_set_files_rlimit(uint32_t nr_vcpus)
@@ -474,7 +476,7 @@ static bool is_guest_memfd_required(struct vm_shape shape)
 struct kvm_vm *__vm_create(struct vm_shape shape, uint32_t nr_runnable_vcpus,
 			   uint64_t nr_extra_pages)
 {
-	uint64_t nr_pages = vm_nr_pages_required(shape.mode, nr_runnable_vcpus,
+	uint64_t nr_pages = vm_nr_pages_required(shape, nr_runnable_vcpus,
 						 nr_extra_pages);
 	struct userspace_mem_region *slot0;
 	struct kvm_vm *vm;
@@ -2334,6 +2336,12 @@ __weak void kvm_arch_vm_post_create(struct kvm_vm *vm)
 {
 }
 
+__weak int kvm_arch_vm_additional_pages_required(struct vm_shape shape,
+						 uint64_t page_size)
+{
+	return 0;
+}
+
 __weak void kvm_selftest_arch_init(void)
 {
 }
-- 
2.34.1