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Message-ID: <aXkEMnDy8UFwJitP@skinsburskii.localdomain>
Date: Tue, 27 Jan 2026 10:30:10 -0800
From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
To: Mukesh R <mrathor@...ux.microsoft.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
decui@...rosoft.com, longli@...rosoft.com,
linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] mshv: Introduce hv_deposit_memory helper functions
On Mon, Jan 26, 2026 at 06:06:23PM -0800, Mukesh R wrote:
> On 1/25/26 14:41, Stanislav Kinsburskii wrote:
> > On Fri, Jan 23, 2026 at 04:33:39PM -0800, Mukesh R wrote:
> > > On 1/22/26 17:35, Stanislav Kinsburskii wrote:
> > > > Introduce hv_deposit_memory_node() and hv_deposit_memory() helper
> > > > functions to handle memory deposition with proper error handling.
> > > >
> > > > The new hv_deposit_memory_node() function takes the hypervisor status
> > > > as a parameter and validates it before depositing pages. It checks for
> > > > HV_STATUS_INSUFFICIENT_MEMORY specifically and returns an error for
> > > > unexpected status codes.
> > > >
> > > > This is a precursor patch to new out-of-memory error codes support.
> > > > No functional changes intended.
> > > >
> > > > Signed-off-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
> > > > ---
> > > > drivers/hv/hv_proc.c | 22 ++++++++++++++++++++--
> > > > drivers/hv/mshv_root_hv_call.c | 25 +++++++++----------------
> > > > drivers/hv/mshv_root_main.c | 3 +--
> > > > include/asm-generic/mshyperv.h | 10 ++++++++++
> > > > 4 files changed, 40 insertions(+), 20 deletions(-)
> > > >
> > > > diff --git a/drivers/hv/hv_proc.c b/drivers/hv/hv_proc.c
> > > > index 80c66d1c74d5..c0c2bfc80d77 100644
> > > > --- a/drivers/hv/hv_proc.c
> > > > +++ b/drivers/hv/hv_proc.c
> > > > @@ -110,6 +110,23 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages)
> > > > }
> > > > EXPORT_SYMBOL_GPL(hv_call_deposit_pages);
> > > > +int hv_deposit_memory_node(int node, u64 partition_id,
> > > > + u64 hv_status)
> > > > +{
> > > > + u32 num_pages;
> > > > +
> > > > + switch (hv_result(hv_status)) {
> > > > + case HV_STATUS_INSUFFICIENT_MEMORY:
> > > > + num_pages = 1;
> > > > + break;
> > > > + default:
> > > > + hv_status_err(hv_status, "Unexpected!\n");
> > > > + return -ENOMEM;
> > > > + }
> > > > + return hv_call_deposit_pages(node, partition_id, num_pages);
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(hv_deposit_memory_node);
> > > > +
> > >
> > > Different hypercalls may want to deposit different number of pages in one
> > > shot. As feature evolves, page sizes get mixed, we'd almost need that
> > > flexibility. So, imo, either we just don't do this for now, or add num pages
> > > parameter to be passed down.
> > >
> >
> > What you do mean by "page sizes get mixed"?
> > A helper to deposit num pages already exists: its
> > hv_call_deposit_pages().
>
> My point, you are removing number of pages, and we may want to keep
> that so one can quickly play around and change them.
>
> - ret = hv_call_deposit_pages(NUMA_NO_NODE,
> - pt_id, 1);
> + ret = hv_deposit_memory(pt_id, status);
>
> For example, in hv_call_initialize_partition() we may realize after
> some analysis that depositing 2 pages or 4 pages is much better.
>
We have been using this 1-page deposit logic from the beginning. To
change the number of pages, simply replace hv_deposit_memory with
hv_call_deposit_pages and specify the desired number of pages.
The proposed approach reduces code duplication and is less error-prone,
as there are multiple error codes to handle. Consolidating the logic
also makes the driver more robust.
Thanks, Stanislav
> > Thanks,
> > Stanislav
> >
> > > Thanks,
> > > -Mukesh
> > >
> > >
> > >
> > > > bool hv_result_oom(u64 status)
> > > > {
> > > > switch (hv_result(status)) {
> > > > @@ -155,7 +172,8 @@ int hv_call_add_logical_proc(int node, u32 lp_index, u32 apic_id)
> > > > }
> > > > break;
> > > > }
> > > > - ret = hv_call_deposit_pages(node, hv_current_partition_id, 1);
> > > > + ret = hv_deposit_memory_node(node, hv_current_partition_id,
> > > > + status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -197,7 +215,7 @@ int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags)
> > > > }
> > > > break;
> > > > }
> > > > - ret = hv_call_deposit_pages(node, partition_id, 1);
> > > > + ret = hv_deposit_memory_node(node, partition_id, status);
> > > > } while (!ret);
> > > > diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
> > > > index 58c5cbf2e567..06f2bac8039d 100644
> > > > --- a/drivers/hv/mshv_root_hv_call.c
> > > > +++ b/drivers/hv/mshv_root_hv_call.c
> > > > @@ -123,8 +123,7 @@ int hv_call_create_partition(u64 flags,
> > > > break;
> > > > }
> > > > local_irq_restore(irq_flags);
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE,
> > > > - hv_current_partition_id, 1);
> > > > + ret = hv_deposit_memory(hv_current_partition_id, status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -151,7 +150,7 @@ int hv_call_initialize_partition(u64 partition_id)
> > > > ret = hv_result_to_errno(status);
> > > > break;
> > > > }
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE, partition_id, 1);
> > > > + ret = hv_deposit_memory(partition_id, status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -465,8 +464,7 @@ int hv_call_get_vp_state(u32 vp_index, u64 partition_id,
> > > > }
> > > > local_irq_restore(flags);
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE,
> > > > - partition_id, 1);
> > > > + ret = hv_deposit_memory(partition_id, status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -525,8 +523,7 @@ int hv_call_set_vp_state(u32 vp_index, u64 partition_id,
> > > > }
> > > > local_irq_restore(flags);
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE,
> > > > - partition_id, 1);
> > > > + ret = hv_deposit_memory(partition_id, status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -573,7 +570,7 @@ static int hv_call_map_vp_state_page(u64 partition_id, u32 vp_index, u32 type,
> > > > local_irq_restore(flags);
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE, partition_id, 1);
> > > > + ret = hv_deposit_memory(partition_id, status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -722,8 +719,7 @@ hv_call_create_port(u64 port_partition_id, union hv_port_id port_id,
> > > > ret = hv_result_to_errno(status);
> > > > break;
> > > > }
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE, port_partition_id, 1);
> > > > -
> > > > + ret = hv_deposit_memory(port_partition_id, status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -776,8 +772,7 @@ hv_call_connect_port(u64 port_partition_id, union hv_port_id port_id,
> > > > ret = hv_result_to_errno(status);
> > > > break;
> > > > }
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE,
> > > > - connection_partition_id, 1);
> > > > + ret = hv_deposit_memory(connection_partition_id, status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -848,8 +843,7 @@ static int hv_call_map_stats_page2(enum hv_stats_object_type type,
> > > > break;
> > > > }
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE,
> > > > - hv_current_partition_id, 1);
> > > > + ret = hv_deposit_memory(hv_current_partition_id, status);
> > > > } while (!ret);
> > > > return ret;
> > > > @@ -885,8 +879,7 @@ static int hv_call_map_stats_page(enum hv_stats_object_type type,
> > > > return ret;
> > > > }
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE,
> > > > - hv_current_partition_id, 1);
> > > > + ret = hv_deposit_memory(hv_current_partition_id, status);
> > > > if (ret)
> > > > return ret;
> > > > } while (!ret);
> > > > diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> > > > index f4697497f83e..5fc572e31cd7 100644
> > > > --- a/drivers/hv/mshv_root_main.c
> > > > +++ b/drivers/hv/mshv_root_main.c
> > > > @@ -264,8 +264,7 @@ static int mshv_ioctl_passthru_hvcall(struct mshv_partition *partition,
> > > > if (!hv_result_oom(status))
> > > > ret = hv_result_to_errno(status);
> > > > else
> > > > - ret = hv_call_deposit_pages(NUMA_NO_NODE,
> > > > - pt_id, 1);
> > > > + ret = hv_deposit_memory(pt_id, status);
> > > > } while (!ret);
> > > > args.status = hv_result(status);
> > > > diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> > > > index b73352a7fc9e..c8e8976839f8 100644
> > > > --- a/include/asm-generic/mshyperv.h
> > > > +++ b/include/asm-generic/mshyperv.h
> > > > @@ -344,6 +344,7 @@ static inline bool hv_parent_partition(void)
> > > > }
> > > > bool hv_result_oom(u64 status);
> > > > +int hv_deposit_memory_node(int node, u64 partition_id, u64 status);
> > > > int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
> > > > int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
> > > > int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
> > > > @@ -353,6 +354,10 @@ static inline bool hv_root_partition(void) { return false; }
> > > > static inline bool hv_l1vh_partition(void) { return false; }
> > > > static inline bool hv_parent_partition(void) { return false; }
> > > > static inline bool hv_result_oom(u64 status) { return false; }
> > > > +static inline int hv_deposit_memory_node(int node, u64 partition_id, u64 status)
> > > > +{
> > > > + return -EOPNOTSUPP;
> > > > +}
> > > > static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages)
> > > > {
> > > > return -EOPNOTSUPP;
> > > > @@ -367,6 +372,11 @@ static inline int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u3
> > > > }
> > > > #endif /* CONFIG_MSHV_ROOT */
> > > > +static inline int hv_deposit_memory(u64 partition_id, u64 status)
> > > > +{
> > > > + return hv_deposit_memory_node(NUMA_NO_NODE, partition_id, status);
> > > > +}
> > > > +
> > > > #if IS_ENABLED(CONFIG_HYPERV_VTL_MODE)
> > > > u8 __init get_vtl(void);
> > > > #else
> > > >
> > > >
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