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[RFC,kvmtool,08/10] riscv: virtio: Enforce VIRTIO_F_ACCESS_PLATFORM feature flag.

Message ID 20230419222350.3604274-9-atishp@rivosinc.com (mailing list archive)
State Handled Elsewhere
Headers show
Series RISC-V CoVE support | expand

Checks

Context Check Description
conchuod/tree_selection fail Failed to apply to next/pending-fixes or riscv/for-next

Commit Message

Atish Kumar Patra April 19, 2023, 10:23 p.m. UTC 
From: Rajnesh Kanwal <rkanwal@rivosinc.com>

VIRTIO_F_ACCESS_PLATFORM feature tells the guest that device will
be using DMA for transfers. This forces the guest to use DMA API
to allow the host to successfully access guest memory as needed.

This is needed for CoVE VMs.

Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com>
---
 riscv/kvm.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
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Patch

diff --git a/riscv/kvm.c b/riscv/kvm.c
index e728790..aebb6bd 100644
--- a/riscv/kvm.c
+++ b/riscv/kvm.c
@@ -7,6 +7,7 @@ 
 #include <linux/kernel.h>
 #include <linux/kvm.h>
 #include <linux/sizes.h>
+#include <linux/virtio_config.h>
 
 struct kvm_ext kvm_req_ext[] = {
 	{ DEFINE_KVM_EXT(KVM_CAP_ONE_REG) },
@@ -224,5 +225,14 @@  int kvm__arch_setup_firmware(struct kvm *kvm)
 
 u64 kvm__arch_get_virtio_host_features(struct kvm *kvm)
 {
-	return 0;
+	u64 features = 0;
+
+	/* CoVE VMs mandate VIRTIO_F_ACCESS_PLATFORM feature to force use of
+	 * SWIOTLB bounce buffers through DMA API. Without this device probe
+	 * will fail for CoVE VMs.
+	 */
+	if (kvm->cfg.arch.cove_vm)
+		features |= (1ULL << VIRTIO_F_ACCESS_PLATFORM);
+
+	return features;
 }