[PATCH 6.6 573/638] x86/hyperv: Use per cpu initial stack for vtl context

Sasha Levin
2024-03-24T23:10:45Z

From: Saurabh Sengar <ssengar@linux.microsoft.com>

[ Upstream commit 2b4b90e053a29057fb05ba81acce26bddce8d404 ]

Currently, the secondary CPUs in Hyper-V VTL context lack support for
parallel startup. Therefore, relying on the single initial_stack fetched
from the current task structure suffices for all vCPUs.

However, common initial_stack risks stack corruption when parallel startup
is enabled. In order to facilitate parallel startup, use the initial_stack
from the per CPU idle thread instead of the current task.

Fixes: 3be1bc2fe9d2 ("x86/hyperv: VTL support for Hyper-V")
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/1709452896-13342-1-git-send-email-ssengar@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <1709452896-13342-1-git-send-email-ssengar@linux.microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/hyperv/hv_vtl.c | 19 +++++++++++++++----
drivers/hv/Kconfig | 1 +
2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 53b309d41b3b9..c2f78fabc865b 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -12,6 +12,7 @@
#include <asm/i8259.h>
#include <asm/mshyperv.h>
#include <asm/realmode.h>
+#include <../kernel/smpboot.h>

extern struct boot_params boot_params;
static struct real_mode_header hv_vtl_real_mode_header;
@@ -64,7 +65,7 @@ static void hv_vtl_ap_entry(void)
((secondary_startup_64_fn)secondary_startup_64)(&boot_params, &boot_params);
}

-static int hv_vtl_bringup_vcpu(u32 target_vp_index, u64 eip_ignored)
+static int hv_vtl_bringup_vcpu(u32 target_vp_index, int cpu, u64 eip_ignored)
{
u64 status;
int ret = 0;
@@ -78,7 +79,9 @@ static int hv_vtl_bringup_vcpu(u32 target_vp_index, u64 eip_ignored)
struct ldttss_desc *ldt;
struct desc_struct *gdt;

- u64 rsp = current->thread.sp;
+ struct task_struct *idle = idle_thread_get(cpu);
+ u64 rsp = (unsigned long)idle->thread.sp;
+
u64 rip = (u64)&hv_vtl_ap_entry;

native_store_gdt(&gdt_ptr);
@@ -205,7 +208,15 @@ static int hv_vtl_apicid_to_vp_id(u32 apic_id)

static int hv_vtl_wakeup_secondary_cpu(int apicid, unsigned long start_eip)
{
- int vp_id;
+ int vp_id, cpu;
+
+ /* Find the logical CPU for the APIC ID */
+ for_each_present_cpu(cpu) {
+ if (arch_match_cpu_phys_id(cpu, apicid))
+ break;
+ }
+ if (cpu >= nr_cpu_ids)
+ return -EINVAL;

pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid);
vp_id = hv_vtl_apicid_to_vp_id(apicid);
@@ -219,7 +230,7 @@ static int hv_vtl_wakeup_secondary_cpu(int apicid, unsigned long start_eip)
return -EINVAL;
}

- return hv_vtl_bringup_vcpu(vp_id, start_eip);
+ return hv_vtl_bringup_vcpu(vp_id, cpu, start_eip);
}

int __init hv_vtl_early_init(void)
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 00242107d62e0..862c47b191afe 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -16,6 +16,7 @@ config HYPERV
config HYPERV_VTL_MODE
bool "Enable Linux to boot in VTL context"
depends on X86_64 && HYPERV
+ depends on SMP
default n
help
Virtual Secure Mode (VSM) is a set of hypervisor capabilities and
--
2.43.0