KVM ARM Archive on lore.kernel.org
 help / color / Atom feed
From: KarimAllah Ahmed <karahmed@amazon.de>
To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Cc: KarimAllah Ahmed <karahmed@amazon.de>,
	Marc Zyngier <marc.zyngier@arm.com>,
Subject: [PATCH] KVM: arm/arm64: Properly check for MMIO regions
Date: Fri, 12 Jul 2019 10:22:08 +0200
Message-ID: <1562919728-642-1-git-send-email-karahmed@amazon.de> (raw)

Valid RAM can live outside kernel control (e.g. using "mem=" command-line
parameter). This memory can still be used as valid guest memory for KVM. So
ensure that we validate that this memory is definitely not "RAM" before
assuming that it is an MMIO region.

One way to use memory outside kernel control is:

1- Pass 'mem=' in the kernel command-line to limit the amount of memory managed
   by the kernel.
2- Map this physical memory you want to give to the guest with:
   mmap("/dev/mem", physical_address_offset, ..)
3- Use the user-space virtual address as the "userspace_addr" field in

One of the limitations of the current /dev/mem for ARM is that it would map
this memory as uncached without this patch:

This work is similar to the work done on x86 here:

Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Julien Thierry <julien.thierry@arm.com>
Cc: Suzuki K Pouloze <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: kvmarm@lists.cs.columbia.edu
Cc: linux-kernel@vger.kernel.org
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
 virt/kvm/arm/mmu.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 06180c9..2105134 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -8,6 +8,7 @@
 #include <linux/kvm_host.h>
 #include <linux/io.h>
 #include <linux/hugetlb.h>
+#include <linux/memblock.h>
 #include <linux/sched/signal.h>
 #include <trace/events/kvm.h>
 #include <asm/pgalloc.h>
@@ -89,7 +90,7 @@ static void kvm_flush_dcache_pud(struct kvm *kvm,
 static bool kvm_is_device_pfn(unsigned long pfn)
-	return !pfn_valid(pfn);
+	return !memblock_is_memory(__pfn_to_phys(pfn));
@@ -949,6 +950,7 @@ static void stage2_unmap_memslot(struct kvm *kvm,
 	do {
 		struct vm_area_struct *vma = find_vma(current->mm, hva);
 		hva_t vm_start, vm_end;
+		gpa_t gpa;
 		if (!vma || vma->vm_start >= reg_end)
@@ -959,11 +961,14 @@ static void stage2_unmap_memslot(struct kvm *kvm,
 		vm_start = max(hva, vma->vm_start);
 		vm_end = min(reg_end, vma->vm_end);
-		if (!(vma->vm_flags & VM_PFNMAP)) {
-			gpa_t gpa = addr + (vm_start - memslot->userspace_addr);
-			unmap_stage2_range(kvm, gpa, vm_end - vm_start);
-		}
 		hva = vm_end;
+		if ((vma->vm_flags & VM_PFNMAP) &&
+		    !memblock_is_memory(__pfn_to_phys(vma->vm_pgoff)))
+			continue;
+		gpa = addr + (vm_start - memslot->userspace_addr);
+		unmap_stage2_range(kvm, gpa, vm_end - vm_start);
 	} while (hva < reg_end);
@@ -2329,7 +2334,8 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 		vm_start = max(hva, vma->vm_start);
 		vm_end = min(reg_end, vma->vm_end);
-		if (vma->vm_flags & VM_PFNMAP) {
+		if ((vma->vm_flags & VM_PFNMAP) &&
+		    !memblock_is_memory(__pfn_to_phys(vma->vm_pgoff))) {
 			gpa_t gpa = mem->guest_phys_addr +
 				    (vm_start - mem->userspace_addr);
 			phys_addr_t pa;

kvmarm mailing list

             reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-12  8:22 KarimAllah Ahmed [this message]
2019-07-12 15:58 ` Raslan, KarimAllah

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1562919728-642-1-git-send-email-karahmed@amazon.de \
    --to=karahmed@amazon.de \
    --cc=kvmarm@lists.cs.columbia.edu \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=marc.zyngier@arm.com \


* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM ARM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvmarm/0 kvmarm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvmarm kvmarm/ https://lore.kernel.org/kvmarm \
		kvmarm@lists.cs.columbia.edu kvmarm@archiver.kernel.org
	public-inbox-index kvmarm

Newsgroup available over NNTP:

AGPL code for this site: git clone https://public-inbox.org/ public-inbox