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arm64: kvm: Fix IDMAP overlap with HYP VA 

Booting 5.4 on LX2160A reveals that KVM is non-functional:

kvm: Limiting the IPA size due to kernel Virtual Address limit
kvm [1]: IPA Size Limit: 43bits
kvm [1]: IDMAP intersecting with HYP VA, unable to continue
kvm [1]: error initializing Hyp mode: -22

Debugging shows:

kvm [1]: IDMAP page: 81a26000
kvm [1]: HYP VA range: 0:22ffffffff

as RAM is located at:

80000000-fbdfffff : System RAM
2080000000-237fffffff : System RAM

Comparing this with the same kernel on Armada 8040 shows:

kvm: Limiting the IPA size due to kernel Virtual Address limit
kvm [1]: IPA Size Limit: 43bits
kvm [1]: IDMAP page: 2a26000
kvm [1]: HYP VA range: 4800000000:493fffffff
...
kvm [1]: Hyp mode initialized successfully

which indicates that hyp_va_msb is set, and is always set to the
opposite value of the idmap page to avoid the overlap. This does not
happen with the LX2160A.

Further debugging shows vabits_actual = 39, kva_msb = 38 on LX2160A and
kva_msb = 33 on Armada 8040. Looking at the bit layout of the HYP VA,
there is still one bit available for hyp_va_msb. Set this bit
appropriately. This allows KVM to be functional on the LX2160A, but
without any HYP VA randomisation:

kvm: Limiting the IPA size due to kernel Virtual Address limit
kvm [1]: IPA Size Limit: 43bits
kvm [1]: IDMAP page: 81a24000
kvm [1]: HYP VA range: 4000000000:62ffffffff
...
kvm [1]: Hyp mode initialized successfully

Fixes: ed57cac83e ("arm64: KVM: Introduce EL2 VA randomisation")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
[maz: small additional cleanups, preserved case where the tag
 is legitimately 0 and we can just use the mask, Fixes tag]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/E1ilAiY-0000MA-RG@rmk-PC.armlinux.org.uk
This commit is contained in:
Russell King 2019-12-28 11:57:14 +00:00 committed by Marc Zyngier
parent 5f675c56ed
commit f5523423de
1 changed files with 25 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

56
arch/arm64/kvm/va_layout.c
View File

@ -13,52 +13,46 @@
#include <asm/kvm_mmu.h>
/*
* The LSB of the random hyp VA tag or 0 if no randomization is used.
* The LSB of the HYP VA tag
*/
static u8 tag_lsb;
/*
* The random hyp VA tag value with the region bit if hyp randomization is used
* The HYP VA tag value with the region bit
*/
static u64 tag_val;
static u64 va_mask;
/*
* We want to generate a hyp VA with the following format (with V ==
* vabits_actual):
*
* 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0
* ---------------------------------------------------------
* | 0000000 | hyp_va_msb | random tag | kern linear VA |
* |--------- tag_val -----------|----- va_mask ---|
*
* which does not conflict with the idmap regions.
*/
__init void kvm_compute_layout(void)
{
phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
u64 hyp_va_msb;
int kva_msb;
/* Where is my RAM region? */
hyp_va_msb = idmap_addr & BIT(vabits_actual - 1);
hyp_va_msb ^= BIT(vabits_actual - 1);
kva_msb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^
tag_lsb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^
(u64)(high_memory - 1));
if (kva_msb == (vabits_actual - 1)) {
/*
* No space in the address, let's compute the mask so
* that it covers (vabits_actual - 1) bits, and the region
* bit. The tag stays set to zero.
*/
va_mask = BIT(vabits_actual - 1) - 1;
va_mask |= hyp_va_msb;
} else {
/*
* We do have some free bits to insert a random tag.
* Hyp VAs are now created from kernel linear map VAs
* using the following formula (with V == vabits_actual):
*
* 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0
* ---------------------------------------------------------
* | 0000000 | hyp_va_msb | random tag | kern linear VA |
*/
tag_lsb = kva_msb;
va_mask = GENMASK_ULL(tag_lsb - 1, 0);
tag_val = get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb);
tag_val |= hyp_va_msb;
tag_val >>= tag_lsb;
va_mask = GENMASK_ULL(tag_lsb - 1, 0);
tag_val = hyp_va_msb;
if (tag_lsb != (vabits_actual - 1)) {
/* We have some free bits to insert a random tag. */
tag_val |= get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb);
}
tag_val >>= tag_lsb;
}
static u32 compute_instruction(int n, u32 rd, u32 rn)
@ -117,11 +111,11 @@ void __init kvm_update_va_mask(struct alt_instr *alt,
* VHE doesn't need any address translation, let's NOP
* everything.
*
* Alternatively, if we don't have any spare bits in
* the address, NOP everything after masking that
* kernel VA.
* Alternatively, if the tag is zero (because the layout
* dictates it and we don't have any spare bits in the
* address), NOP everything after masking the kernel VA.
*/
if (has_vhe() || (!tag_lsb && i > 0)) {
if (has_vhe() || (!tag_val && i > 0)) {
updptr[i] = cpu_to_le32(aarch64_insn_gen_nop());
continue;
}