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Message-ID: <5980eaf9-2e77-d0ec-e39b-b48913c8b72f@microsoft.com>
Date: Thu, 20 Feb 2025 21:59:27 +0000
From: MUKESH RATHOR <mukeshrathor@...rosoft.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "linux-arch@...r.kernel.org"
<linux-arch@...r.kernel.org>, "iommu@...ts.linux.dev"
<iommu@...ts.linux.dev>, "mhklinux@...look.com" <mhklinux@...look.com>,
"eahariha@...ux.microsoft.com" <eahariha@...ux.microsoft.com>
CC: KY Srinivasan <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
"catalin.marinas@....com" <catalin.marinas@....com>, "will@...nel.org"
<will@...nel.org>, "tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>, "x86@...nel.org"
<x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>, "joro@...tes.org"
<joro@...tes.org>, "robin.murphy@....com" <robin.murphy@....com>,
"arnd@...db.de" <arnd@...db.de>, "jinankjain@...ux.microsoft.com"
<jinankjain@...ux.microsoft.com>, "muminulrussell@...il.com"
<muminulrussell@...il.com>, "skinsburskii@...ux.microsoft.com"
<skinsburskii@...ux.microsoft.com>
Subject: Re: [PATCH v2 2/3] hyperv: Change hv_root_partition into a function
On 2/20/25 10:33, Nuno Das Neves wrote:
> Introduce hv_current_partition_type to store the partition type
> as an enum.
>
> Right now this is limited to guest or root partition, but there will
> be other kinds in future and the enum is easily extensible.
>
> Set up hv_current_partition_type early in Hyper-V initialization with
> hv_identify_partition_type(). hv_root_partition() just queries this
> value, and shouldn't be called before that.
>
> Making this check into a function sets the stage for adding a config
> option to gate the compilation of root partition code. In particular,
> hv_root_partition() can be stubbed out always be false if root
> partition support isn't desired.
>
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> ---
> arch/arm64/hyperv/mshyperv.c | 2 ++
> arch/x86/hyperv/hv_init.c | 10 ++++-----
> arch/x86/kernel/cpu/mshyperv.c | 24 ++------------------
> drivers/clocksource/hyperv_timer.c | 4 ++--
> drivers/hv/hv.c | 10 ++++-----
> drivers/hv/hv_common.c | 35 +++++++++++++++++++++++++-----
> drivers/hv/vmbus_drv.c | 2 +-
> drivers/iommu/hyperv-iommu.c | 4 ++--
> include/asm-generic/mshyperv.h | 15 +++++++++++--
> 9 files changed, 61 insertions(+), 45 deletions(-)
>
> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> index 29fcfd595f48..2265ea5ce5ad 100644
> --- a/arch/arm64/hyperv/mshyperv.c
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -61,6 +61,8 @@ static int __init hyperv_init(void)
> ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
> ms_hyperv.misc_features);
>
> + hv_identify_partition_type();
> +
> ret = hv_common_init();
> if (ret)
> return ret;
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 9be1446f5bd3..ddeb40930bc8 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -90,7 +90,7 @@ static int hv_cpu_init(unsigned int cpu)
> return 0;
>
> hvp = &hv_vp_assist_page[cpu];
> - if (hv_root_partition) {
> + if (hv_root_partition()) {
> /*
> * For root partition we get the hypervisor provided VP assist
> * page, instead of allocating a new page.
> @@ -242,7 +242,7 @@ static int hv_cpu_die(unsigned int cpu)
>
> if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
> union hv_vp_assist_msr_contents msr = { 0 };
> - if (hv_root_partition) {
> + if (hv_root_partition()) {
> /*
> * For root partition the VP assist page is mapped to
> * hypervisor provided page, and thus we unmap the
> @@ -317,7 +317,7 @@ static int hv_suspend(void)
> union hv_x64_msr_hypercall_contents hypercall_msr;
> int ret;
>
> - if (hv_root_partition)
> + if (hv_root_partition())
> return -EPERM;
>
> /*
> @@ -518,7 +518,7 @@ void __init hyperv_init(void)
> rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> hypercall_msr.enable = 1;
>
> - if (hv_root_partition) {
> + if (hv_root_partition()) {
> struct page *pg;
> void *src;
>
> @@ -592,7 +592,7 @@ void __init hyperv_init(void)
> * If we're running as root, we want to create our own PCI MSI domain.
> * We can't set this in hv_pci_init because that would be too late.
> */
> - if (hv_root_partition)
> + if (hv_root_partition())
> x86_init.irqs.create_pci_msi_domain = hv_create_pci_msi_domain;
> #endif
>
> diff --git a/arch/x86/kernel/cpu/mshyperv.c
b/arch/x86/kernel/cpu/mshyperv.c
> index f285757618fc..4f01f424ea5b 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -33,8 +33,6 @@
> #include <asm/numa.h>
> #include <asm/svm.h>
>
> -/* Is Linux running as the root partition? */
> -bool hv_root_partition;
> /* Is Linux running on nested Microsoft Hypervisor */
> bool hv_nested;
> struct ms_hyperv_info ms_hyperv;
> @@ -451,25 +449,7 @@ static void __init ms_hyperv_init_platform(void)
> pr_debug("Hyper-V: max %u virtual processors, %u logical
processors\n",
> ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);
>
> - /*
> - * Check CPU management privilege.
> - *
> - * To mirror what Windows does we should extract CPU management
> - * features and use the ReservedIdentityBit to detect if Linux is the
> - * root partition. But that requires negotiating CPU management
> - * interface (a process to be finalized). For now, use the privilege
> - * flag as the indicator for running as root.
> - *
> - * Hyper-V should never specify running as root and as a Confidential
> - * VM. But to protect against a compromised/malicious Hyper-V trying
> - * to exploit root behavior to expose Confidential VM memory, ignore
> - * the root partition setting if also a Confidential VM.
> - */
> - if ((ms_hyperv.priv_high & HV_CPU_MANAGEMENT) &&
> - !(ms_hyperv.priv_high & HV_ISOLATION)) {
> - hv_root_partition = true;
> - pr_info("Hyper-V: running as root partition\n");
> - }
> + hv_identify_partition_type();
>
> if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) {
> hv_nested = true;
> @@ -618,7 +598,7 @@ static void __init ms_hyperv_init_platform(void)
>
> # ifdef CONFIG_SMP
> smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
> - if (hv_root_partition ||
> + if (hv_root_partition() ||
> (!ms_hyperv.paravisor_present && hv_isolation_type_snp()))
> smp_ops.smp_prepare_cpus = hv_smp_prepare_cpus;
> # endif
> diff --git a/drivers/clocksource/hyperv_timer.c
b/drivers/clocksource/hyperv_timer.c
> index f00019b078a7..09549451dd51 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -582,7 +582,7 @@ static void __init hv_init_tsc_clocksource(void)
> * mapped.
> */
> tsc_msr.as_uint64 = hv_get_msr(HV_MSR_REFERENCE_TSC);
> - if (hv_root_partition)
> + if (hv_root_partition())
> tsc_pfn = tsc_msr.pfn;
> else
> tsc_pfn = HVPFN_DOWN(virt_to_phys(tsc_page));
> @@ -627,7 +627,7 @@ void __init hv_remap_tsc_clocksource(void)
> if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
> return;
>
> - if (!hv_root_partition) {
> + if (!hv_root_partition()) {
> WARN(1, "%s: attempt to remap TSC page in guest partition\n",
> __func__);
> return;
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index fab0690b5c41..a38f84548bc2 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -144,7 +144,7 @@ int hv_synic_alloc(void)
> * Synic message and event pages are allocated by paravisor.
> * Skip these pages allocation here.
> */
> - if (!ms_hyperv.paravisor_present && !hv_root_partition) {
> + if (!ms_hyperv.paravisor_present && !hv_root_partition()) {
> hv_cpu->synic_message_page =
> (void *)get_zeroed_page(GFP_ATOMIC);
> if (!hv_cpu->synic_message_page) {
> @@ -272,7 +272,7 @@ void hv_synic_enable_regs(unsigned int cpu)
> simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
> simp.simp_enabled = 1;
>
> - if (ms_hyperv.paravisor_present || hv_root_partition) {
> + if (ms_hyperv.paravisor_present || hv_root_partition()) {
> /* Mask out vTOM bit. ioremap_cache() maps decrypted */
> u64 base = (simp.base_simp_gpa << HV_HYP_PAGE_SHIFT) &
> ~ms_hyperv.shared_gpa_boundary;
> @@ -291,7 +291,7 @@ void hv_synic_enable_regs(unsigned int cpu)
> siefp.as_uint64 = hv_get_msr(HV_MSR_SIEFP);
> siefp.siefp_enabled = 1;
>
> - if (ms_hyperv.paravisor_present || hv_root_partition) {
> + if (ms_hyperv.paravisor_present || hv_root_partition()) {
> /* Mask out vTOM bit. ioremap_cache() maps decrypted */
> u64 base = (siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT) &
> ~ms_hyperv.shared_gpa_boundary;
> @@ -367,7 +367,7 @@ void hv_synic_disable_regs(unsigned int cpu)
> * addresses.
> */
> simp.simp_enabled = 0;
> - if (ms_hyperv.paravisor_present || hv_root_partition) {
> + if (ms_hyperv.paravisor_present || hv_root_partition()) {
> iounmap(hv_cpu->synic_message_page);
> hv_cpu->synic_message_page = NULL;
> } else {
> @@ -379,7 +379,7 @@ void hv_synic_disable_regs(unsigned int cpu)
> siefp.as_uint64 = hv_get_msr(HV_MSR_SIEFP);
> siefp.siefp_enabled = 0;
>
> - if (ms_hyperv.paravisor_present || hv_root_partition) {
> + if (ms_hyperv.paravisor_present || hv_root_partition()) {
> iounmap(hv_cpu->synic_event_page);
> hv_cpu->synic_event_page = NULL;
> } else {
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 2120aead98d9..c5c5dc92ff21 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -34,8 +34,11 @@
> u64 hv_current_partition_id = HV_PARTITION_ID_SELF;
> EXPORT_SYMBOL_GPL(hv_current_partition_id);
>
> +enum hv_partition_type hv_current_partition_type;
> +EXPORT_SYMBOL_GPL(hv_current_partition_type);
> +
nit: if possible and not too late, can we please use more Unix
style naming, eg, hv_curr_ptid and hv_curr_pt_type rather than this
long windows style names that causes unnecessary line wraps/splits.
Thanks,
-Mukesh
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